Pull v1.1 out of the api_url and create a new method resources_url

I like the ability to get the url based on a token for the object type, but linked object's URLs from the responses already contain the v1.1 so if it's in the api_base, we can't use Clever.request to resolve link uris properly.
Implement district.schools. This needs to be generalized into all associations for all objects
Implement school.sections. This is another instance of the associated object code that needs to be abstracted.