Version 0.2

This is a Beta version for Clients. You would expect that the clients works well enough for daily use.

• OAuthClient is refactored to be the base class for Flask and Django.
• Add Django integrations authlib.client.django.OAuth and authlib.client.django.RemoteApp.
• Refactor on authlib.client.flask.OAuth and authlib.client.flask.RemoteApp.
• Refactor on Ready to Use Apps, make it stable and ready to use.