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/__init__.py

@@ -0,0 +1,35 @@
+"""
+oauthlib.oauth2
+~~~~~~~~~~~~~~
+
+This module is a wrapper for the most recent implementation of OAuth 2.0 Client
+and Server classes.
+"""
+from .rfc6749.clients import (
+    BackendApplicationClient, Client, LegacyApplicationClient,
+    MobileApplicationClient, ServiceApplicationClient, WebApplicationClient,
+)
+from .rfc6749.endpoints import (
+    AuthorizationEndpoint, BackendApplicationServer, IntrospectEndpoint,
+    LegacyApplicationServer, MetadataEndpoint, MobileApplicationServer,
+    ResourceEndpoint, RevocationEndpoint, Server, TokenEndpoint,
+    WebApplicationServer,
+)
+from .rfc6749.errors import (
+    AccessDeniedError, FatalClientError, InsecureTransportError,
+    InvalidClientError, InvalidClientIdError, InvalidGrantError,
+    InvalidRedirectURIError, InvalidRequestError, InvalidRequestFatalError,
+    InvalidScopeError, MismatchingRedirectURIError, MismatchingStateError,
+    MissingClientIdError, MissingCodeError, MissingRedirectURIError,
+    MissingResponseTypeError, MissingTokenError, MissingTokenTypeError,
+    OAuth2Error, ServerError, TemporarilyUnavailableError, TokenExpiredError,
+    UnauthorizedClientError, UnsupportedGrantTypeError,
+    UnsupportedResponseTypeError, UnsupportedTokenTypeError,
+)
+from .rfc6749.grant_types import (
+    AuthorizationCodeGrant, ClientCredentialsGrant, ImplicitGrant,
+    RefreshTokenGrant, ResourceOwnerPasswordCredentialsGrant,
+)
+from .rfc6749.request_validator import RequestValidator
+from .rfc6749.tokens import BearerToken, OAuth2Token
+from .rfc6749.utils import is_secure_transport