title: Initialize a Rails 3 plugin gem on installation
body: <p>I'm creating a RubyGem, and I'm wondering if there's any way I can set it up so that when it's listed in a <code>Gemfile</code> and someone runs <code>bundle install</code>, my gem can copy some files into the Rails path. This would save the user from having to type <code>rails generate blah</code>, where <code>blah</code> is the name of a generator in my gem.</p>
  
  <p>Is there a callback that the current version of Bundler runs when it installs a gem?</p>