Total users metrics shouldn't be separated into weeks for USSD app

It looks like the ghr ussd js app is separating the metrics fired for users into weeks (the metric looks something like `ghr_ussd_total_users_<week>`). I think this needs to be changed to simply increment the total users (so the name should like something like `ghr_ussd_total_users`). The app does not have to worry about splitting up the metrics into different weeks, diamondash and graphite will handle this.

https://github.com/praekelt/go-nike-ghr/blob/develop/js_sandbox/lib/go-nike-ghr.js#L532