Add script to award steam badges retroactively and notify CSOL-site of these awards

NOTE:  OPENBADGER_NOTIFICATION_WEBHOOK should now point to '/notify/' instead of '/notify/claim'.  e.g. 'http://chicagosummeroflearning.org/notify/'

This adds the script award-retroactive-badges, which checks all users to see if they have an unawarded steam badge that they should have been awarded.  If so, it awards them the badge and notifies CSOL-site so that an email may be sent out.

The primary use case for this at the moment is if a data change reduces the requirements for a badge, invalidating the checks that are normally done every time a badge is awarded.

Addresses #258