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/oauth2/rfc6749/__init__.py

@@ -0,0 +1,16 @@
+"""
+oauthlib.oauth2.rfc6749
+~~~~~~~~~~~~~~~~~~~~~~~
+
+This module is an implementation of various logic needed
+for consuming and providing OAuth 2.0 RFC6749.
+"""
+import functools
+import logging
+
+from .endpoints.base import BaseEndpoint, catch_errors_and_unavailability
+from .errors import (
+    FatalClientError, OAuth2Error, ServerError, TemporarilyUnavailableError,
+)
+
+log = logging.getLogger(__name__)