Selenium fixture has better support for navigation fixtures

Given that the selenium fixture is only being used in its tests,
I thought now would be a good time to improve its interface to be
more useful. It can still navigate you to arbitrary URLs, but once
there it is contrained to using a navigation fixture. This allows
for a few assumptions to be made that drastically improve this
fixture's usability.
Updated Toggle VM Script
Merge pull request #159 from jwadkins/updated_toggle_vm

Updated Toggle VM Script
Appliance: Added cert check

Added a certificate check into an appliance testing. The check is parametrized, it takes a list of 2-tuples, filename and md5sum of the file. If md5sum is specified as None, then the file won't be checked against it.
Commits have been squashed.
Merge pull request #160 from mfalesni/upstream

Appliance: Added cert check
Merge pull request #155 from seandst/useful-selenium-fixture

Selenium fixture has better support for navigation fixtures