Revert "Refactor: Use the new Git 2.0 'push --force-with-lease' option"

There were some serious problems with --force-with-lease that caused it to never
push.  I'm not sure what was going on and we needed to make progress so I'm just
going to revert this for now.

See #31 for more information

This reverts commit 200fc9edfe71fc8536fba04d67ae2de5087f32db.