Initial python3 changes

Mostly just updating libraries, removing string encoding/decoding,
fixing some edge cases. No new functionality was added in this
commit.

lib/oauthlib/oauth1/rfc5849/endpoints/__init__.py

@@ -0,0 +1,8 @@
+from .access_token import AccessTokenEndpoint
+from .authorization import AuthorizationEndpoint
+from .base import BaseEndpoint
+from .request_token import RequestTokenEndpoint
+from .resource import ResourceEndpoint
+from .signature_only import SignatureOnlyEndpoint
+
+from .pre_configured import WebApplicationServer  # isort:skip