Pass the mongo uri to abbey.
Set default to 'amis' just like in stage_release.py
Add nginx to the forums role.
Set a default value for nginx_default_sites.
Change how the deployment gets updated.
Update the deployment document instead of overwriting it.

Since mongo doesn't do recursive updates of complex documents.
Let abbey accept git hashes.
Support noop updates for the deployment collection.
Colon not =
Merge pull request #654 from edx/feanil/pass_mongo

Feanil/pass mongo