Add tests_require into setup.py

pytest and mock are needed for running tests.

This needs to be redone; will do so at a later stage.

Closes #28.

As Handler objects can have multiple sockets, we need to know which one
was involved in the incoming event.

Don't pass auto back.

Broken and not been maintained in some time. See #21.

Fix bug in tproxy recv_udp() method.

importlib is Python 2.7 only.

Is Python 2.x only. Not supported under Python 3.x.

Pull out firewall methods code into seperate files.

Fix problems starting with method=='auto'; we were making decisions
based on the method, before the method had been finalized by the
firewall.

Only very basic testing so far. What could go wrong?

Was broken by passing environment variable PYTHONPATH to process. Will
fix this if there is a use case for it.

* Make compatible with setuptools.
* Load modules via ssh into separate modules, not the one name space.