Update tox.ini gevent dependencies once it supports PyPy and Python3

[rgalanakis]

tox.ini uses the tip of surfly/gevent for PyPy because 1.0.1 doesn't support it.

Much worse, the 3.3 environment is a total mess, because Cython wouldn't install before gevent on travis, so cython is in deps, and gevent is installed as a command. However the removal of gevent as a dependency meant that setup,py egg_info couldn't be run (explicit backend set but not valid raises error), so the GOLESS_BACKEND var is nulled out. To top off the cake, travis couldn't find coverage, so tox just runs nosetests.

Rather than debug this crap (I tried!), let's just wait for gevent.