GIFCasting

Fixes #32, making animated GIFs for Atom. If we want to add any other apps, we can add those in another PR.

Requisite demo of embedded animated gifs:

![creaturefeature](https://f.cloud.github.com/assets/836375/2340833/362c430a-a4cb-11e3-8d30-ec67e81f738d.gif)

![externallice](https://f.cloud.github.com/assets/836375/2340894/c38413a8-a4cc-11e3-9e6e-02f75642507a.gif)