Severed last ties between Resource and Django

[ElSaico]

build_response now throws a NotImplementedError by default, while request_method and request_body are not called "Django-specific" on the documentation since multiple subclasses use them as-is.

Making it pure WSGI by default would need a separate Resource (hint!), since it needs to wrap the entire request-response cycle.

[coveralls]

Coverage increased (+0.7%) to 96.714% when pulling 27859c8 on CraveFood:generic-resource into a4994eb on toastdriven:master.

[coveralls]

Coverage increased (+0.7%) to 96.714% when pulling 27859c8 on CraveFood:generic-resource into a4994eb on toastdriven:master.