Use older unittest methods to allow testing in python 2.6, 2.5

A couple of minor changes which allowed me to confirm that the test suite for pyhtml passes fully in Python 2.6 and 2.5:

$ python2.6 tests.py
....................................
----------------------------------------------------------------------
Ran 36 tests in 0.004s

OK

$ python2.5 tests.py
....................................
----------------------------------------------------------------------
Ran 36 tests in 0.005s

OK