big @mentions update

1. switched from autocomplete.js to jquery-textcomplete
2. style update
3. Allow mentioning by ign OR display name
4. display names can be two words and separated by a space
5. display names can be all characters, except a few special ones (punctuation etc)
6. Wildcard characters are escaped in SQL
7. Suggestions are html escaped
8. Suggestions have a timeout of 300ms, so the query is made after you stopped typing

app/assets/stylesheets/application.css

@@ -3,4 +3,5 @@
  *= require style.css
  *= require mobi.css
  *= require highlight/default.css
+ *= require jquery-textcomplete
  */