Support additional log levels

We should support a debug mode. So, first make all logs go to same
logger - not loggers named by their module. Then add a -d flag to the
shell arguments. And finally, start to differentiate log levels in the
code itself.
Fix incorrect function call

Errantly called this as set_debug instead of set_level_debug.
Merge pull request #13 from craigtracey/morelogging

Support additional log levels