More optional fields.

1.0.4

More optionals.

Made extra properties optional.

Merge pull request #3 from vapor-community/response-fix

Made extra properties optional.

Check for created and noContent 2xx responses and not just ok

Merge pull request #2 from vapor-community/response-fix

Check for potential 2xx responses messagebird can return.

Made `MessagebirdClient` init public

Merge pull request #1 from vapor-community/public-init

Make client init public.

Initial release

Initial release.
Supports only the SMS API currently.