adding napa_reserve cli and deploy task

Updating the deploy task so that it takes `force` flag and will also accept an optional `sha`.

To make this work I added an executable called `napa_reserve`. This pulls in all the regular napa cli tools and adds anything new from napa_reserve. I'm sort of looking at this like a place where things can be built out and tested before they get merged into napa proper. The plan would be to merge this into napa soon. With this change we can now do:

```
napa_reserve deploy production
napa_reserve deploy production --force # so that local changes won't prevent you from being able to deploy
napa_reserve deploy production --revision=abc123 # useful when we need to rollback a bad deploy
```

@jdoconnor @danielmackey @kevinreedy @shanesveller