User balance calc

I've added a utility class to calculate the balance for a specific user and distributor. Note that balances only make sense specific to a distributor as per the discussions in: 
https://github.com/openfoodfoundation/openfoodnetwork/issues/297

Erm.... noob question though. I guess I've added some commits to master accidentally that are now included in this branch. Of particular annoyance is report_download_namechange...
Whats the best way to revert these changes so they drop off this branch? Any links to instructions appreciated :-)