title: Rails Install Fails Due To Invalid Option: --include-dependencies
body: <p>Trying to install rails on a new Mac I just got.  I enter:</p>
  
  <pre><code>sudo gem install rails --include-dependencies
  </code></pre>
  
  <p>But it produces:</p>
  
  <pre><code>ERROR:  While executing gem ... (OptionParser::InvalidOption)
  invalid option: --include-dependencies
  </code></pre>
  
  <p>If I run it without the include dependencies, I get other errors that seem to be related to dependencies.  Why would this option not work for me but it does others?  Is there another option I can include which will instal all the dependencies?</p>
  
  <p>Note: I'm new to Linux/Mac/Rails/Gems, etc.  </p>
  
  <p>Thanks</p>