Add Activity feed view

Adds a flagged off Activity pane.

![](http://f.cl.ly/items/0b0U1Q3j0c143I0P1b2b/Image%202014-11-07%20at%204.16.19%20PM.png)
I feel like `depth` is only going to work properly for components of the same type. E.g. depth will work for views reacting to views, but not views reacting to modules. `patchAppComponentTrigger` is called with every component we listen to, and each one of those will create a closure with its own `depth` reference. In order for depth to work across components, it should be accessible via the agent, and JavaScript's single-threaded nature + Backbone's synchronicity of events should keep it consistent.