Fix some "make format" issue

Summary:
* make sure when some pre-check fails, the script won't halt immediately.
* change fburl to google's short url.
* Fix a bug in this script: now it checks the uncommitted code only.

Test Plan: Ran the script under differnet environments.

Reviewers: igor

Reviewed By: igor

CC: leveldb

Differential Revision: https://reviews.facebook.net/D15231