Fixes lack of tracebacks in error emails

This upgrades gevent to 1.0rc2 in order to fix the lack of tracebacks in error notification emails.  Have to build from github.

See:

- https://groups.google.com/forum/?fromgroups=#!topic/gevent/hdCT8cddnrw
- https://github.com/benoitc/gunicorn/issues/214
- http://pypi.python.org/pypi/gevent

My process for testing:

1. Put an exception in the reports homepage view.
2. Using existing virtualenv, run ./manage.py run_gunicorn as specified in services/templates/supervisor_django.conf, using services/gunicorn.cfg.
3. Get an error email with no traceback.
4. run pip install -r requirements/requirements.txt
5. Rerun run_gunicorn
6. Get an error email with traceback

gevent 1.0 has a lot of implementation changes so we should check that nothing would break.