title: How to open a gem source code with bundler in vim editor
body: <p>Trying to open a gem source code with <code>bundle open</code> command, <a href="http://bundler.io/v1.3/bundle_open.html">according to official documentation and instruction</a>.</p>
  
  <p>So, I <code>exported</code> editor like this in <code>.profile</code>: </p>
  
  <pre><code>export BUNDLER_EDITOR=vi
  export EDITOR=vi 
  </code></pre>
  
  <p>And try to open e.g. <code>rails</code> source code using console: </p>
  
  <pre><code>bundle open rails 
  </code></pre>
  
  <p>and getting error <code>Could not locale Gemfile</code> </p>
  
  <pre><code>[ruby-2.1.1] 
  [~/]
   $: rails -v 
  Rails 4.0.3
  [ruby-2.1.1] 
  [~/]
   $: bundle -v 
  Bundler version 1.5.3
  [ruby-2.1.1] 
  [~/]
   $: bundle open rails 
  Could not locate Gemfile
  [ruby-2.1.1] 
  [~/]
   $: 
  </code></pre>
  
  <p>What is missing in this steps ? How do open rails source code using bundler.</p>