IDNotRegistered exception can now be printed.

* A couple errors preventing the __str__() function from returning
  correctly.
Fixed bug in pytest_redis that ran things twice.

* Each test function was being run twice accidently, which was messing
  things up considerably.
Fixed some more issues with pytest plugin.

* The output wasn't being captured properly, now it should be.
Implemented a couple more functions and tests.

* vmfactory_grab has a couple of tests pointed at it now.
* Started on a higher-level workflow test that will pretend to be a
  vmfactory and go through the commands it would normally go through.
  There's still a few functions necessary to get that working.