Token revocation

[reginafcompton]

Finish implementation of /oauth/revoke endpoint.

authserver/authserver/api/oauth2.py

Lines 74 to 75 in d804447

	def post(self):
	return authorization.create_endpoint_response('revocation')

[reginafcompton]

N.b., this is not high priority, since tokens will expire without our intervention. However, we should consider getting this implemented before deploying Facet to production.