Update to ST3, switch to symlinks for settings

[Sublime Text 3](http://www.sublimetext.com/3) is now in open beta, and [Package Control](https://sublime.wbond.net/) 2.0 has shipped. Both of these upgrades introduce significant shifts in the Sublime Text world. Let's take advantage of a few of them.

Before, due to ST2 being weird with symlinks, `sublime2/copy` was necessary to sync up user settings and preferences. Now, with ST3, I've successfully switched the system to using symlinks, making it much cleaner. ST3 also has a more streamlined preferences system (all user prefs should go in user settings - never touch system settings), so there are fewer files to sync.

What's more, we can also sync packages with Package Control. In this PR, I'm symlinking `Package Control.sublime-settings`, which, upon startup, ST3 + Package Control will automatically install any missing packages.

Finally, this PR also updates the `bin/subl` to point to ST3.

Overall, I think this cleans up the Sublime Text dotfiles a bit, in addition to bumping us to ST3. If you have any issues, or aren't ready to jump to ST3 yet, let me know.