Update to allow for full-width $ in cashtags

[comp615]

Latin: $$$ Full width: ＄＄＄ Small: ﹩﹩﹩ (We could consider the small size hashtag add too)

Should be a simple add here: https://github.com/twitter/twitter-text-rb/blob/master/lib/twitter-text/regex.rb#L284

We already do this for hashtags elsewhere: https://github.com/twitter/twitter-text-rb/blob/master/lib/twitter-text/regex.rb#L165