title: Heroku does not accept push even though I have sqlite in development block
body: <p>I have the following lines in my <code>Gemfile</code>:</p>
  
  <pre><code>gem 'rails', '3.1.1'
  
  group :production do
    gem 'pg'
  end        
  
  group :development, :test do
    gem 'sqlite3'
  end
  </code></pre>
  
  <p>I also ran <code>bundle install</code> to have my <code>Gemfile.lock</code> updated.</p>
  
  <p>When I push to heroku I still get the following error:</p>
  
  <pre><code> !
   !     Failed to install gems via Bundler.
   !     
   !     Detected sqlite3 gem which is not supported on Heroku.
   !     http://devcenter.heroku.com/articles/how-do-i-use-sqlite3-for-development
   !
   !     Heroku push rejected, failed to compile Ruby/rails app
  </code></pre>
  
  <p>What am I missing?</p>