Single sign on login support, part one

This provides the beginnings to SSO login:

1) Canvas create user to ensure the accounts stay in sync (subject to change with team discussions on finalizing this design. Currently tries to enroll in course too.)

2) A method for the CAS server to check credentials. Needed for sso to work at all.

3) It does NOT use the CAS server for main platform itself. That will be a separate part two PR.
On Wed, Sep 24, 2014 at 01:46:24PM -0700, Brian Sadler wrote:
> I have a task on the backlog to make this more secure against brute force attacks.  Should be fine for the short term though.

yeah, there's a few options we could do like need a secret shared key that isn't too hard. It would reject everything unless that password is included in the request. Then we add that to the configuration on the rubycas and bz environments and boom.