Implemented multi part upload for large mongo dumps. Added option to run backup on a cron style interval.

If there is a mongo dump that's over 4 GB it will be send over in multiple chunks.
You can run backups as a cron style (via rufus scheduler) to run at a certain time every day/night no matter when you started your script.
Mongo dump is deleted once the gzip file is created (to save space).
Adding some documentation and aborting upload whenever there are errors

Documentation that I am adding is based on my production environment running an outdated Fog gem so this might not apply to most people but it might help someone else.
Merge pull request #2 from lovegandhi/multi_part_upload

Multi part upload and cron style scheduler