Add driver for HiSt

Here's a driver for HiST, which is also employing Feide / SAML, slightly different from NTNU. This ought to be very easy to adapt to other schools. 

However, it just _seems_ to work - the output from the last request() is the dashboard, and everything should be fine. However, any subsequent request (ie. loading the inbox) causes a redirect to /log_out.aspx?SessionExpired=0. 

I figured I'd send you a PR just in case I'm overlooking a trivial fix. If not, then perhaps someone else with HiST credentials could give it a look, or change the parameters to match their school.