Fix some font loading issues and py3 string conversions.
Run 2to3 on tests
TESTS: Raise ValueError in GraphicsContextArray.__init__

Test was expecting ValueError, but an AssertionError was being
raised.
Also added kiva/tests/__init__.py so tat tests can be run from
installation.
Tests: Fix tests for running on python 3.

All unit tests now pass on python 3.3 and 2.7 on linux.
Few integration tests segfault, as was the case before.