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 
It's a special Vagrant upstart event (https://github.com/mitchellh/vagrant/blob/7897de3fbdc4c61a281954ec2df1c23bfe22f4d4/plugins/guests/ubuntu/cap/mount_nfs.rb#L13).  Unfortunately it doesn't seem to be documented on their website.