title: Why can't I build an ER Diagram for my Rails app using the rails-erd gem?
body: <p>I'm on Mac OSX 10.10 (Yosemite)
  I'm following the really simple instructions to run graphviz <a href="http://voormedia.github.io/rails-erd/install.html" rel="nofollow"><strong>here</strong></a> so that I can get an Entity-Relationship diagram for my Rails App.</p>
  
  <p>But it is not working:</p>
  
  <pre><code>$ brew install graphviz
  ==&gt; Downloading https://downloads.sf.net/project/machomebrew/Bottles/graphviz-2.38.0.yosemite.bottle.1.tar.gz
  Already downloaded: /Library/Caches/Homebrew/graphviz-2.38.0.yosemite.bottle.1.tar.gz
  ==&gt; Pouring graphviz-2.38.0.yosemite.bottle.1.tar.gz
    /usr/local/Cellar/graphviz/2.38.0: 469 files, 68M
  
  # Now I added gem 'rails-erd' to the Gemfile
  
  $ bundle install 
  &lt;&lt; SNIPPED SOME EXTRANEOUS OUTPUT HERE &gt;&gt;
  Updating files in vendor/cache
    * choice-0.1.6.gem
    * ruby-graphviz-1.0.9.gem
    * rails-erd-1.1.0.gem
  Your bundle is complete!
  Use `bundle show [gemname]` to see where a bundled gem is installed.
  
  $ bundle show rails-erd
  /Users/myuser/.rvm/gems/ruby-1.9.3-p484@my-app-dir/gems/rails-erd-1.1.0
  
  $ bundle exec rake erd --trace
  rake aborted!
  Don't know how to build task 'erd'
  /Users/myuser/.rvm/gems/ruby-1.9.3-p484@my-app-dir/gems/rake-10.0.4/lib/rake/task_manager.rb:49:in `[]'
  /Users/myuser/.rvm/gems/ruby-1.9.3-p484@my-app-dir/gems/rake-10.0.4/lib/rake/application.rb:142:in `invoke_task'
  /Users/myuser/.rvm/gems/ruby-1.9.3-p484@my-app-dir/gems/rake-10.0.4/lib/rake/application.rb:101:in `block (2 levels) in top_level'
  </code></pre>
  
  <p>Why doesn't the rake file know about the <code>erd</code> task?? I did <code>bundle exec rake -T</code> and it doesn't show up there.</p>