Added logging to ditto

Summary: Rather than using bare print statements to display information, ditto uses the python logging module. This allows it to separate different types of info and let the user control verbosity.

Test Plan: ad-hoc, ran tests in testing directory

Reviewers: ankur, nikita, adam, pieguy, carl

CC: engineering

Differential Revision: http://grizzly.memsql.com/D2967