List emojis by name

This ensure the grammar only matches emojis that actually exist.

Closes #8
Prepare 0.20.0 release
Use quantifiers for number of * and __
:lipstick: Label entire match
Update spec description to be more accurate
Add support for bold italic text

Wrapped in either *** or ___

Closes #7
Prepare 0.21.0 release
Merge branch 'master' into add-ordered-list

Conflicts:
	grammars/gfm.cson