Adding HOST, PORT, and PYTHON_PATH config options in ``settings.py``

I had to setup some more options in the settings.py, maybe you will be interested by those. 
The default behavior is kept.

The 2 commit diffs are very small and summary line is quite self explanatory.

Thanks for rsted ! Very helpfull ! Just decided to install it on my server after being using http://rst.ninjs.org/ until recently when it broke with '502 Bad Gateway' message.

I hope this last part is not new information for you BTW.