Client settings

- Adding support for rollbar client settings `hostWhitelist` and `ignoredMessages`
- Moved `client_api_key` into the `client_settings` hash.

Additionally, this `client_settings` is a breaking change, so maybe it's time we move smoke_detector to 1.0.0.
oic. I got confused since the variable name changed from `client` to `client_settings` as you follow it through the callstack