Python logging by default sends all output to stderr, but that's not what
normal programs usually do and is not expected for these scripts.
Change the ubuntutools.getLogger() method to return a logger with handlers
correctly set up to send INFO level (or lower) logs to stdout and WARNING
level (or higher; technically INFO+1 level or higher) logs to stderr.
This results in normally logged output going to stdout and warnings/errors
going to stderr, as expected.
