OS X support

Seeing as your Sublime Text Cookbook is the only one in the chef-marketplace, and wanting to avoid proliferating a ton of duplicate cookbooks, I decided to fork off of your cookbook and add OS X support to it (instead of creating a whole new cookbook for it).

In order to allow for multi-OS support I went ahead and implemented a pattern which I developed while working for Pagoda Box which helped keep the code more organized.

I also changed the version dependency for apt (removing the trailing zero) so that it will continue to be compatible with apt 2.6.  Hopefully that's not an issue.

I regret to admit that I didn't write any automated tests for this since I'm targeting OS X and don't have the expensive VM Ware plugin for Vagrant.  Hopefully that's OK.  I have tested it repeatedly with both Sublime 2 & 3 on my personal Mac.

Let me know if there's anything else you'd like adjusted or if the whole thing won't do for some reason.  Thanks!