Just `HTTPS POST /edx-mobile-api/v1/registrar/myu.mydept.mycourse.t2_2014/userid` to register and `HTTPS DELETE /edx-mobile-api/v1/registrar/myu.mydept.mycourse.t2_2014/userid` to unregister would be more in line w/ REST and how @singingwolfboy and I are constructing the new api.