Add support for python 2.6

Summary:
Python 2.6 does not have argparse installed by default,
so we use optparse instead.

Test Plan: Ran on machine with 2.6 and on another one with 2.7

Reviewers: jack

Reviewed By: jack

Subscribers: Diffs_emails

Differential Revision: http://phabricator.signalfuse.com/D3458