Adjust factory method to follow Flask extension guidelines
Adjust test for `init_app`
Merge branch 'factory-fix' of https://github.com/mattupstate/flask-restful into mattupstate-factory-fix

Conflicts:
	flask_restful/__init__.py
	tests/test_api.py
Merge pull request #222 from twilio/mattupstate-factory-fix

Mattupstate factory fix