Use logging lib for messages

Instead of just calling print() to print messages, I would suggest to use the [logging](http://docs.python.org/3.2/library/logging.html) library for better logging capabilities, such as different logging levels (info, warning, error, debug), timestamps, log to syslog or other handlers, etc. For start, a simple handler to write to sys.stdout can be implemented.

What do you think?
