Downgraded to Python 2.7 to use eventlet

Ultimately I'd like to experiment with integrating this project into
OpenStack which is still based on Python 2.x and uses eventlet for
pretty much everything.
Add nose as a test runner.

To run the tests:

    $ python setup.py test

or, if you need to use nose plugins

    $ python setup.py nosetests --nose-options ...
Workaround bug when using nose collector for tests.

When running

    $ python setup.py test

an error is raised:

    Error in atexit._run_exitfuncs:
    Traceback (most recent call last):
      File "/usr/lib/python2.7/atexit.py", line 24, in _run_exitfuncs
        func(*targs, **kargs)
      File "/usr/lib/python2.7/multiprocessing/util.py", line 284, in _exit_function
        info('process shutting down')
    TypeError: 'NoneType' object is not callable
    Error in sys.exitfunc:
    Traceback (most recent call last):
      File "/usr/lib/python2.7/atexit.py", line 24, in _run_exitfuncs
        func(*targs, **kargs)
      File "/usr/lib/python2.7/multiprocessing/util.py", line 284, in _exit_function
        info('process shutting down')
    TypeError: 'NoneType' object is not callable

See: http://bugs.python.org/issue15881#msg170215
Add testing instructions to documentation.
Merge pull request #1 from smoynes/feature/nosetests

Use nosetests as test collector