Fix tox.ini

It was caused by several things:

 * I am pretty sure the PYTHONPATH in the tox.ini was not needed
 * I also reduced it to one [testenv] section, shared by both environments
 * it actually failed on python3 because wsgiref was in the requirements.txt and failed to install

It is now working, at least not blowing up, the only thing is the python 3 tests are failing, but since you are switching to nose in another branch, I will leave that upto you.