title: assets:precompile connects to DB when initialize_on_precompile is false
body: <p>I have <code>config.assets.initialize_on_precompile = false</code> in my <code>config/application.rb</code> and <code>bundle exec rake assets:precompile</code> still attempts to connect to my DB. I changed my db name in <code>database.yml</code> to a non-existent database so I can tell when it's trying to connect.</p>
  
  <pre><code>$ be rake assets:precompile
  rake aborted!
  FATAL:  database "aaa" does not exist
  </code></pre>