Initial gem build

This is the initial build of the `napa_reserve` gem. It basically does 2 things right now:

1) Logs all gems in use by a service. Details here: https://github.com/bellycard/platform/issues/138
2) Reports deprecation warnings. Right now this is external from Napa because Napa upgrades to some services could cause things to break (we saw this with email recently). Eventually, this would probably get moved into Napa proper. Example:

```
DEPRECATION WARNING: Use of Grape::Entity is discouraged, please transition your code to Roar representers - https://github.com/bellycard/napa/blob/master/docs/grape_entity_to_roar.md. (called from <top (required)> at app/entities/addon_entity.rb:1)
```

@jdoconnor @danielmackey @kevinreedy @shanesveller

cc: @ajself @shayhowe