title: How to update ruby gem dependency? Must I rebuild it? How?
body: <p>I have a gem already installed locally, and I wanna add a new dependency into it. I worked with below steps:</p>
  
  <ol>
  <li>Open the gem installation folder as below:<br>
  <code>/usr/local/rvm/gems/ruby-2.1.0/gems/nesta-0.10.0</code></li>
  <li>Add new dependency below into gemspec file (nesta.gemspec)<br>
  <code>s.add_dependency('stacktracer', '&gt;= 0.0.1')</code></li>
  <li>Append <code>gem 'stacktracer'</code> into <code>Gemfile</code></li>
  <li>Add <code>require "stacktracer"</code> into <code>Rakefile</code></li>
  <li>Run command <code>bundle update nesta</code></li>
  <li>Run command <code>bundle install</code></li>
  <li>Check <code>Gemfile.lock</code>, I already found the new dependency like below:</li>
  </ol>
  
  <p>I have next dependencies:</p>
  
  <pre><code>DEPENDENCIES
  debugger
  mr-sparkle (&gt;= 0.0.2)
  nesta!
  rack-test (= 0.6.1)
  rspec (~&gt; 2.14.0)
  **stacktracer**
  test-unit (= 1.2.3)
  webrat (~&gt; 0.7.3)
  </code></pre>
  
  <p>But when I met two problems here:</p>
  
  <ol>
  <li>run command <code>gem dependency nesta</code>, I did not find stacktracer dependency list.</li>
  <li><p>I added <code>require "stacktracer"</code> into <code>app.rb</code>, then run the application, it failed due to below error:</p>
  
  <pre><code>/usr/local/rvm/gems/ruby-2.1.0/gems/nesta-0.10.0/lib/nesta/app.rb:4:in `require': cannot load such file -- stacktracer (LoadError)
  </code></pre></li>
  </ol>
  
  <p>Could any one help me to tackle the problems? Is there any approach that could manage to update gem dependency successfully?</p>