Add an Emoji Typeahead
This adds a more complete emoji datasource, with a typeahead and autocomplete. It works by pulling in a raw datasource from EmojiOne (I chose Unicode 8, but they have a Unicode 9 datasource as well) and transforming it for speed/need. If we build more robustness or an actual picker into the Remarkup bar, having the additional keywords, etc, might be important. When Unicode 9 support is more prevalent, we should only need to update the single file.
Tossing up as a proof of concept on engineering direction. Also I can't quite get the autocomplete to complete.
Test Plan: Test UIExamples, Autocomplete, and TypeaheadSource
Reviewed By: epriestley
Maniphest Tasks: T12139
Differential Revision: https://secure.phabricator.com/D17244