Feature: Display full path on hover

This adds a simple full display of truncated paths on hover.

Screenshot:

![screen shot 2014-01-22 at 9 51 47 pm](https://f.cloud.github.com/assets/808159/1982143/f5027c94-83f2-11e3-9614-162614398244.png)

/cc @hueniverse @wpreul @thegoleffect