Refactor to improve completion support & snippets

Hey all, it's time to test this new branch before merging into master.

See Changelog for details:
https://github.com/danro/LESS-sublime/blob/6a7bf54da7ea0eb98b5f8045f8b198470239a07e/readme.md#changelog

You'll need to manually clone and check out `refactor`
https://github.com/danro/LESS-sublime/tree/refactor

Tested and working on the following platforms:
* OSX 10.8 - Sublime 2 / 3
* Win7 x64 - Sublime 2 / 3

Please report any test results or feedback in this thread.

Once merged, this will close #12, #21
cc @posabsolute @chadwhitaker @kanni @sethne @DjebbZ @mannieschumpert @xhacker @Deeh-kz @aziz