Use mozlog instead of raw print statements

I hope I used mozlog well - I looked at mozversion source as an example.
So two problems with this:

1. getLogger is the old API, not the new structured one we should be using.
2. I think it would be better to get logging objects on demand and add them to our classes on construction using get_default_logger() API:

http://mozbase.readthedocs.org/en/latest/mozlog_structured.html#mozlog.structured.structuredlog.get_default_logger