Fixing auth issues... for real this time

resolves #95 -- I really think this fixes it this time... minor tweaks
to async vs. synchronous use of authenticate() methods and some
significant tests of the api auth methods seems to have done the
trick... See APIClientTest.cs' new combo auth pattern tests (bad/good,
good/good) reauth process which i think addresses the powershell issue
here... you can auth as many times as you want now and the singleton
really doesn't care... I may add something in there to laugh at you b/c
you're attempting to auth too many times... that's the point of the
singleton... but it works now