Update plugin to work with Hapi v17

[mringer]

As I'm sure you're aware Hapi v17 contains breaking changes for plugins and auth as well as the depreciation of callbacks and the introduction of async-await support. This PR includes changes that bring hapi-auth-firebase current with Hapi v17.

• Version bump to 1.1.0 (or whatever you think the next version should be)

• Update the plugin registration signature to conform to v17 API plugins [server.register()](https://github.com/hapijs/hapi/blob/083c7b1536019b678fc7d43fa5ecb90ff8078ac3/API.md#server.register())

• Update Auth scheme to work with new v17 API [server.auth.scheme()](https://github.com/hapijs/hapi/blob/083c7b1536019b678fc7d43fa5ecb90ff8078ac3/API.md#server.auth.scheme()) [h.unauthenticated()](https://github.com/hapijs/hapi/blob/083c7b1536019b678fc7d43fa5ecb90ff8078ac3/API.md#h.unauthenticated())

• Update tests to conform to v17 plugin.register() API -- drop callback from register function

[mringer]

@dsdenes bump

[mringer]

Bump @dsdenes

[imcodingideas]

@dsdenes bump?