Atom packages can load cson grammars and TextMate packages can't
Move scoped properties out of the grammar file and into a directory

Closes #435
Update GFM snippets to atom syntax instead of textmate
Replace LoadTextMatePackagesTask with async grammar loading
Use `atom.activatePackage` directly in specs
Remove auto-indentation for markdown files

Closes #395

@kevinsawicki I couldn't figure out a reason for this
indent pattern? I looked in the TextMate package and I
didn't see it there either.
Remove auto-indent gfm spec
Parse emoji start, word, and end into different scopes
Add link segment to GFM underline scope
Include JS/CoffeeScript grammars in markdown code blocks
Add language name to fenced scopes
Include css grammar in fenced block
Include XML grammar for fenced XML blocks
Include ruby grammar for fenced ruby blocks
Include Java grammar in fenced code blocks
Include $self inside heading rule

This allows emoji, links, etc. to be parsed
and highlighted in headings
Include source.shell inside of sh/bash code blocks
Allow more than 3 back ticks for fenced code blocks
Add a description for each package
Add mdown for GFM fileTypes