Watch Files

Watch for file changes, then refresh the tiles (via SSE triggered event client side).  This make editing using another text editor a lot easier. 

I wouldn't say this is finished, it's a bit hacky and I dont know the tm2 codebase well, but I wanted to prototype the idea. 

![tm2-watch-fs](https://cloud.githubusercontent.com/assets/26278/3100081/b1a514d8-e60e-11e3-89fe-f5da6a8e00d8.gif)

cc: @yhahn @edenh @camilleanne