Enable use of `python setup.py test` with Distribute.

This change causes 308 of the 314 total unit tests to be run (and
run successfully so) under Python 2.7.  This is a first attempt.
We still need to get the doctests included and running.

setup.py

@@ -79,6 +79,7 @@ setup(name='pystache',
       url='http://github.com/defunkt/pystache',
       packages=['pystache'],
       license='MIT',
+      test_suite='pystache.tests',
       entry_points = {
         'console_scripts': ['pystache=pystache.commands:main'],
       },