Remove need for setUpClass/tearDownClass

This has two big advantages. Firsts, we don't need to worry about someone creating a test that needs the ZMQ ioloop without remembering to call setUpClass of the base class. Second, now we can do 'python setup.py test' from Py2.6
Merge pull request #612 from scottkmaxwell/fix-test_stream-when-run-standalone

Remove need for setUpClass/tearDownClass