Bundler installs sqlite3 every time, but there's not sqlite in Gemfile

Bundler keeps install sqlite3 every time, but i'm not using it in my project. I've chosen Postgres, but can not deploy it to Heroku. Bundler is the reason for that. Why it is? And what should i do?

I was trying to make separate gemset for that. I cleared and reinstalled all gems. But every time sqlite comes to my "bundle install" log:

.......
Using sqlite3 (1.3.4) 
Using sqlite3-ruby (1.3.3) 
Using taps (0.3.23) 
Using thin (1.2.11) 
Using turn (0.8.2) 
Using uglifier (1.0.3) 
Your bundle is complete! Use `bundle show [gemname]` to see where a bundled gem is installed.

My Gemfile:

source 'http://rubygems.org'

gem 'rails', '3.1.0'

gem "jquery-rails"
gem 'sorcery'
gem 'simple_form'
gem 'cocoon'

gem 'thin'
gem 'heroku'
gem 'taps'
gem 'pg'

# Gems used only for assets and not required
# in production environments by default.
group :assets do
  gem 'sass-rails', "  ~> 3.1.0"
  gem 'coffee-rails', "~> 3.1.0"
  gem 'uglifier'
end

group :development do
  gem "cucumber-rails"
  gem "capybara"
  gem "rspec-rails", ">= 2.0.1"
end

group :test do
  gem 'turn', :require => false
  gem "cucumber-rails"
  gem "capybara"
  gem "rspec-rails", ">= 2.0.1"
  gem "database_cleaner"
  gem "factory_girl_rails"
end

Help pls, what's wrong?

UPDATE: Added Gemfile.lock:

GEM
  remote: http://rubygems.org/
  specs:
    actionmailer (3.1.0)
      actionpack (= 3.1.0)
      mail (~> 2.3.0)
    actionpack (3.1.0)
      activemodel (= 3.1.0)
      activesupport (= 3.1.0)
      builder (~> 3.0.0)
      erubis (~> 2.7.0)
      i18n (~> 0.6)
      rack (~> 1.3.2)
      rack-cache (~> 1.0.3)
      rack-mount (~> 0.8.2)
      rack-test (~> 0.6.1)
      sprockets (~> 2.0.0)
    activemodel (3.1.0)
      activesupport (= 3.1.0)
      bcrypt-ruby (~> 3.0.0)
      builder (~> 3.0.0)
      i18n (~> 0.6)
    activerecord (3.1.0)
      activemodel (= 3.1.0)
      activesupport (= 3.1.0)
      arel (~> 2.2.1)
      tzinfo (~> 0.3.29)
    activeresource (3.1.0)
      activemodel (= 3.1.0)
      activesupport (= 3.1.0)
    activesupport (3.1.0)
      multi_json (~> 1.0)
    addressable (2.2.6)
    ansi (1.3.0)
    arel (2.2.1)
    bcrypt-ruby (3.0.1)
    builder (3.0.0)
    capybara (1.1.1)
      mime-types (>= 1.16)
      nokogiri (>= 1.3.3)
      rack (>= 1.0.0)
      rack-test (>= 0.5.4)
      selenium-webdriver (~> 2.0)
      xpath (~> 0.1.4)
    childprocess (0.2.2)
      ffi (~> 1.0.6)
    cocoon (1.0.12)
    coffee-rails (3.1.1)
      coffee-script (>= 2.2.0)
      railties (~> 3.1.0)
    coffee-script (2.2.0)
      coffee-script-source
      execjs
    coffee-script-source (1.1.2)
    cucumber (1.0.6)
      builder (>= 2.1.2)
      diff-lcs (>= 1.1.2)
      gherkin (~> 2.4.18)
      json (>= 1.4.6)
      term-ansicolor (>= 1.0.6)
    cucumber-rails (1.0.5)
      capybara (>= 1.1.1)
      cucumber (~> 1.0.6)
      nokogiri (>= 1.5.0)
    daemons (1.1.4)
    database_cleaner (0.6.7)
    diff-lcs (1.1.3)
    erubis (2.7.0)
    eventmachine (0.12.10)
    execjs (1.2.8)
      multi_json (~> 1.0)
    factory_girl (2.1.2)
      activesupport
    factory_girl_rails (1.2.0)
      factory_girl (~> 2.1.0)
      railties (>= 3.0.0)
    faraday (0.6.1)
      addressable (~> 2.2.4)
      multipart-post (~> 1.1.0)
      rack (< 2, >= 1.1.0)
    ffi (1.0.9)
    gherkin (2.4.21)
      json (>= 1.4.6)
    heroku (2.8.4)
      launchy (>= 0.3.2)
      rest-client (~> 1.6.1)
      rubyzip
      term-ansicolor (~> 1.0.5)
    hike (1.2.1)
    i18n (0.6.0)
    jquery-rails (1.0.14)
      railties (~> 3.0)
      thor (~> 0.14)
    json (1.6.1)
    json_pure (1.6.1)
    launchy (2.0.5)
      addressable (~> 2.2.6)
    mail (2.3.0)
      i18n (>= 0.4.0)
      mime-types (~> 1.16)
      treetop (~> 1.4.8)
    mime-types (1.16)
    multi_json (1.0.3)
    multipart-post (1.1.3)
    nokogiri (1.5.0)
    oauth (0.4.5)
    oauth2 (0.4.1)
      faraday (~> 0.6.1)
      multi_json (>= 0.0.5)
    pg (0.11.0)
    polyglot (0.3.2)
    rack (1.3.3)
    rack-cache (1.0.3)
      rack (>= 0.4)
    rack-mount (0.8.3)
      rack (>= 1.0.0)
    rack-ssl (1.3.2)
      rack
    rack-test (0.6.1)
      rack (>= 1.0)
    rails (3.1.0)
      actionmailer (= 3.1.0)
      actionpack (= 3.1.0)
      activerecord (= 3.1.0)
      activeresource (= 3.1.0)
      activesupport (= 3.1.0)
      bundler (~> 1.0)
      railties (= 3.1.0)
    railties (3.1.0)
      actionpack (= 3.1.0)
      activesupport (= 3.1.0)
      rack-ssl (~> 1.3.2)
      rake (>= 0.8.7)
      rdoc (~> 3.4)
      thor (~> 0.14.6)
    rake (0.9.2)
    rdoc (3.9.4)
    rest-client (1.6.7)
      mime-types (>= 1.16)
    rspec (2.6.0)
      rspec-core (~> 2.6.0)
      rspec-expectations (~> 2.6.0)
      rspec-mocks (~> 2.6.0)
    rspec-core (2.6.4)
    rspec-expectations (2.6.0)
      diff-lcs (~> 1.1.2开发者_StackOverflow社区)
    rspec-mocks (2.6.0)
    rspec-rails (2.6.1)
      actionpack (~> 3.0)
      activesupport (~> 3.0)
      railties (~> 3.0)
      rspec (~> 2.6.0)
    rubyzip (0.9.4)
    sass (3.1.7)
    sass-rails (3.1.2)
      actionpack (~> 3.1.0)
      railties (~> 3.1.0)
      sass (>= 3.1.4)
      sprockets (~> 2.0.0)
      tilt (~> 1.3.2)
    selenium-webdriver (2.7.0)
      childprocess (>= 0.2.1)
      ffi (>= 1.0.7)
      json_pure
      rubyzip
    sequel (3.20.0)
    simple_form (1.5.2)
      actionpack (~> 3.0)
      activemodel (~> 3.0)
    sinatra (1.0)
      rack (>= 1.0)
    sorcery (0.6.1)
      bcrypt-ruby (~> 3.0.0)
      oauth (~> 0.4.4)
      oauth (~> 0.4.4)
      oauth2 (~> 0.4.1)
      oauth2 (~> 0.4.1)
    sprockets (2.0.0)
      hike (~> 1.2)
      rack (~> 1.0)
      tilt (!= 1.3.0, ~> 1.1)
    sqlite3 (1.3.4)
    sqlite3-ruby (1.3.3)
      sqlite3 (>= 1.3.3)
    taps (0.3.23)
      rack (>= 1.0.1)
      rest-client (< 1.7.0, >= 1.4.0)
      sequel (~> 3.20.0)
      sinatra (~> 1.0.0)
      sqlite3-ruby (~> 1.2)
    term-ansicolor (1.0.6)
    thin (1.2.11)
      daemons (>= 1.0.9)
      eventmachine (>= 0.12.6)
      rack (>= 1.0.0)
    thor (0.14.6)
    tilt (1.3.3)
    treetop (1.4.10)
      polyglot
      polyglot (>= 0.3.1)
    turn (0.8.2)
      ansi (>= 1.2.2)
    tzinfo (0.3.29)
    uglifier (1.0.3)
      execjs (>= 0.3.0)
      multi_json (>= 1.0.2)
    xpath (0.1.4)
      nokogiri (~> 1.3)

PLATFORMS
  ruby

DEPENDENCIES
  capybara
  cocoon
  coffee-rails (~> 3.1.0)
  cucumber-rails
  database_cleaner
  factory_girl_rails
  heroku
  jquery-rails
  pg
  rails (= 3.1.0)
  rspec-rails (>= 2.0.1)
  sass-rails (~> 3.1.0)
  simple_form
  sorcery
  taps
  thin
  turn
  uglifier

(Even though you've figured it out, i'll put it here incase for some reason people don't read the comments)

The 'taps' gem (http://rubygems.org/gems/taps) that you've required in your Gemfile has a runtine dependancy on the 'sqlite3-ruby' gem.

You can ususally find out where strange dependencies come from by looking in your Gemfile.lock file, as you can see here...

taps (0.3.23)
  rack (>= 1.0.1)
  rest-client (< 1.7.0, >= 1.4.0)
  sequel (~> 3.20.0)
  sinatra (~> 1.0.0)
  sqlite3-ruby (~> 1.2)

Each gem will be listed with its runtime dependencies along with the version that it needs.