Quick Timer hack

This is a very, very, very rough draft, but achieves the general purpose of an on-screen, fixed 5 minute timer for use when presenting.

Next iterations need an adjustable time range, but this suffices for a first attempt.

![timer-demo](https://cloud.githubusercontent.com/assets/352082/4313327/618af2a8-3ec7-11e4-84bc-bf749281d2fa.gif)