Touchstone-auth

Added
- Added the ability to control cookiejar saving. Autosave can be disabled
and the session cookies can now be saved at any time, not just on close.

Added
- Added the ability to do initial authentication with username/password
or with Kerberos tickets.
Deprecated
- Passing the certfile/cert password as their own arguments is now deprecated.
Use the new `auth_type` argument to pass authentication information.
New contributors
- Nickolai Zeldovich (zeldovich)

Added
- Added the ability to load a wider variety of Bearer tokens (Tim tickets)

Added
- Added the ability to use phone-call second factor.
- Added additional constructor argument to select between
available second factor options.
- Added typing-extensions to dependencies to properly support
Python 3.6 and Python 3.7

Added
- First working version of the touchstone auth.