Cross-browser flexbox sticky footer

Firefox:
![firefox](https://f.cloud.github.com/assets/583202/2251728/ecf8ad90-9d9f-11e3-82a1-4b15f09e2440.png)

Chrome:
![chrome](https://f.cloud.github.com/assets/583202/2251729/efe608b8-9d9f-11e3-97d9-72f07ee51241.png)

Safari:
![safari](https://f.cloud.github.com/assets/583202/2251730/f2ec1dfe-9d9f-11e3-9a35-c715ad2072e1.png)

IE8:
![ie8](https://f.cloud.github.com/assets/583202/2251733/f65d70fa-9d9f-11e3-8823-40b2ab85f59d.png)

IE9:
![ie9](https://f.cloud.github.com/assets/583202/2251736/f8e6b980-9d9f-11e3-99ef-869078ac21ff.png)

IE10:
![ie10](https://f.cloud.github.com/assets/583202/2251737/fcc00a3e-9d9f-11e3-95a5-1b97db4deac5.png)

IE11:
![ie11](https://f.cloud.github.com/assets/583202/2251739/fff10302-9d9f-11e3-869e-50e4ae587572.png)

Close enough.

:monkey: