Allow services to extend the API.

Services can extend the API. There are a few things the service needs to
do:

1) Create an 'api.py' file which contains the "Resource" they are using
for the API.
2) Create a 'urls.py' (if it doesn't already have one) and add a
function to it called "register_api()". The function should look like
this:

    def register_api(v1_api):
        from my_service.api import MyServiceResource
        v1_api.register(MyServiceResource())

When the API registers its URLs your service's API URLs will be
included.

One thing to keep in mind is that your service will most likely already
have a MongoEngine class for handling its own collection in the
database. You should use that class in your Resource. If your service
works on a specific CRITs top-level object, you might need that class.
If it works on multiple top-level objects, have fun :)
Merge branch 'master' into service_api_extension
Update urls.py

Rename 'foo' variable.
Merge pull request #148 from crits/service_api_extension

Allow services to extend the API