[Piglit] Convert framework unittests to nose

[Dylan Baker]

Nose is a much better unittesting platform for python. Much, much, much
better. USing nose has a lot of advantages:

1) It doesn't uses classes as containers and other horrible reuse of OO
   elements of python for code seperation, which makes the test clear
   and easy to write; they're just python functions.
2) It doesn't require a script to use. Simplying running nosetsts
   framework/tests is all there is to it.
3) It provides lots of useful functionality natively: fixtures, test
   generators, plugins