Add tooltip to Admin & Moderator glyph

Added tooltip to Admin & Moderator glyph ([relevant meta topic](https://meta.discourse.org/t/add-tooltips-to-admin-moderator-fontawesome-glyphs-in-topic-view/15548)).

![glyph-tooltip](https://cloud.githubusercontent.com/assets/5732281/3264085/6df44af6-f27a-11e3-9580-73a823caf917.png)