Use mozlog instead of raw print statements

I hope I used mozlog well - I looked at mozversion source as an example.
1. Ok! I must have looked at an old code base version of mozversion. but still, there is the old api too: http://dxr.mozilla.org/mozilla-central/source/testing/mozbase/mozversion/mozversion/mozversion.py#32.
2. Well I'm used to global loggers, and find them very convenient - I'm afraid that this design could leave to boilerplate code - I'll give it a try!