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/5732281/3263846/51c971c4-f277-11e3-9a43-9af822b90a38.png)