Fix upstart scripts to only start when dependent services are up

Should ensure that after running `vagrant reload`, the `celeryd`, `tiler`, and `ecoservice` jobs will be running.

Fixes #21 
Hm. Are these `upstart` events, or OS events? It might be a good idea to throw in a one line comment "# bind to upstart events:" to these `.conf` files, because I doubt the average person working on this project is going to know what these are at first glance.