title: "Failed to extract git version" CocoaPods using Mac
body: <p>I need some help. I am trying to install CocoaPods to my mac and I receive the following error when I get to the "pod setup" part of the process. Any ideas?</p>
  
  <pre><code>Nathans-MacBook-Air:~ nathannoel$ pod setup --verbose
  
  /Library/Ruby/Gems/2.3.0/gems/cocoapods-1.5.3/lib/cocoapods/command.rb:118:in 
  `git_version': Failed to extract git version from `git --version`
  ("xcrun: error: invalid active developer path
    (/Applications/Xcode.app/Contents/Developer), missing xcrun at: 
     /Applications/Xcode.app/Contents/Developer/usr/bin/xcrun\n") (RuntimeError)
    from /Library/Ruby/Gems/2.3.0/gems/cocoapods-1.5.3/lib/cocoapods/command.rb:130:in 
   `verify_minimum_git_version!'
    from /Library/Ruby/Gems/2.3.0/gems/cocoapods-1.5.3/lib/cocoapods/command.rb:49:in `run'
    from /Library/Ruby/Gems/2.3.0/gems/cocoapods-1.5.3/bin/pod:55:in `&lt;top (required)&gt;'
    from /usr/local/bin/pod:22:in `load'
    from /usr/local/bin/pod:22:in `&lt;main&gt;'
  
  Nathans-MacBook-Air:~ nathannoel$
  </code></pre>