Clarify dependencies of SnakeberryService

[nichtich]

I am not familiar with Python, but according to http://www.tornadoweb.org tornado requires Python 2.6 and according to https://pypi.python.org/pypi/simplejson/ simplejson is included in Python 2.6, so I think one could remove the dependency to simplejson.

[salendron]

Thanks for you hint! I am a bit busy with projects irght now, but as soon as I have time for Snakeberry again I will clean up the dependencies!

Thanks again for your support!