Overhaul make-tag
Overhaul make-tag

This fixes a bunch of things in make-tag to make it easier to use:

1. it figures out the correct remote since we don't all have "origin"
   as the remote name
2. it tells you more about what it's going to do before it does it
3. it prompts you before it does things--this gives you a chance to
   say, "OH NO!!! DON'T DO THAT!!!" before triggering a deploy

mozilla-services/tecken,mozilla-services/tecken,mozilla-services/tecken,mozilla-services/tecken