Add test kitchen support, with cavaets

This commit adds initial test kitchen support to this cookbook.

* It assumes that those who wish to use test-kitchen have a box named
  `macosx-10.9` already built and added on their local workstation.
  Said box should not have anything installed - it should be a base OS.
* build-essential is added via a Berksfile and included before
  `homebrew`, as it's required by homebrew (the project), but not by
  homebrew (this cookbook), since users may wish to install XCode on
  their own systems via the App Store.
Merge pull request #54 from opscode-cookbooks/jtimberman/test-kitchen

Add test kitchen support, with cavaets