move relengapi.testing to relengapi.tests.context
Add general support for testing subcommands
move subcommands to relengapi.lib.testing, since it's a part of the API
move TestContext to relengapi.lib.testing.context, since it's part of the blueprint API
bump up required coverage
Merge djmitche/build-relengapi:testing-utils (PR #113)

Conflicts:
	base/relengapi/blueprints/badpenny/test_badpenny.py
	base/relengapi/blueprints/base/__init__.py
	base/relengapi/blueprints/docs/test_docs.py
	base/relengapi/blueprints/tokenauth/test_tokenauth.py
	base/relengapi/tests/test_angular.py
	base/relengapi/tests/test_api.py
	base/relengapi/tests/test_celery.py
	base/relengapi/tests/test_db.py
	base/relengapi/tests/test_lib_auth.py
	base/relengapi/tests/test_lib_auth_browserid.py
	base/relengapi/tests/test_lib_auth_external.py
	base/relengapi/tests/test_lib_permissions.py
	base/relengapi/tests/test_proxy.py
	base/relengapi/tests/test_subcommands.py
	base/relengapi/tests/test_util.py