Add Wall display

This wasn't a feature requested explicitly, but one we use, so I figured I'd publish this and see if there's any desire to include it in the upstream. At my company we display CI status on TV's that run in our office. This CL adds a wall display (a 3rd tab that now sits between "Dashboard" and "Settings" in the navigation.

![alt text](http://i.imgur.com/QsBw7V4.png "Wall display")

Build changes are reported via websocket, so a build will appear here in realtime once it has started. The changes are published over hubs that have the form `wall/user/:userid` or `wall/team/:teamid` in order to keep them organized.  Recent builds are shown in each block with the topmost being the recent build that shows overall build health. This is design with a 1080p television in mind currently, which limits the projects to 6. The last recently used project will be bumped from the display.

A few notes on the implementation: 

* We used Angular for building the UI, which is a departure from the rest of the project. I used the Google CDN link for Angular because `go.rice` seemed to choke when including Angular for whatever reason. 
* Because we used Angular, the initial list of projects is done via an AJAX handler that serves up the same list of commits as the relevant dashboard. This is as opposed to the project-common practice of doing this in the template.
* We didn't explicitly match styles to the rest of Drone. We did this because, based on testing on a display that needed to be viewed from a distance, his was our idea of what worked best.
* The icon fonts are GPL (https://github.com/Keyamoon/IcoMoon--limited-)