Support for python 3.4

[nikksbagul]

Hi,

I'm trying out the boshclient.py and I get the following error:

response = sasl.process(base64.b64decode(challenge))

File "/opt/pyvirtualenv/py_3.4_dj_1.9/lib/python3.4/site-packages/puresasl/client.py", line 15, in wrapped
return f(self, _args, *_kwargs)
File "/opt/pyvirtualenv/py_3.4_dj_1.9/lib/python3.4/site-packages/puresasl/client.py", line 141, in process
return self._chosen_mech.process(challenge)
File "/opt/pyvirtualenv/py_3.4_dj_1.9/lib/python3.4/site-packages/puresasl/mechanisms.py", line 407, in process
setattr(self, key, challenge_dict[key])
TypeError: attribute name must be string, not 'bytes'