Add font-awesome

for all the icons used in Aloha (Off the top of my head: warning, link, edit, remove, settings, external-link, paragraph, image, table, certificate).

https://github.com/oerpub/Aloha-Editor/pull/150 has been upgraded to Font-Awesome 4.1 as well

glyphicon contains icons for warning, link, edit, remove, settings, image, table, certificate (missing paragraph, numbered-list, table)

Fixes #144