add :simple_smile: to 😄 emoji for Slack compatibility

2014-2015 emojis (http://www.unicode.org/emoji/charts/full-emoji-list.html)

fix line brake bug

Faster encode technique

Conflicts:
	lib/rumoji/emoji/symbols.rb

Ignore arbitrary strings wrapped in colons

fix colon with emoji problem

This is a fix for #7.
In addition to the updated iterator, I've adjusted the numeric emoji to
use accurate unicode codepoints.

Make decode regex work with codes that have dashes in them

Handle some edge cases with "possible emoji"

Don't strip characters that match the first codepoints in multi-codepoint emoji in Rumoji.encode_io

[ci skip]

Fixes #1