Add Flowdock integration.

Embeds the GIF in a message sent to the Inbox for the given API token.

Tested this out locally. Anything I missed?

Screenshot:
![screen shot 2014-07-03 at 12 47 06 pm](https://cloud.githubusercontent.com/assets/785208/3474990/0dd1963e-02eb-11e4-9e6f-fdf5f9e01659.png)