Removed the `gateway.s3.bucket` setting because the S3 gateway is deprecated

See <https://github.com/elasticsearch/elasticsearch/issues/2458>

If you want to use the S3 gateway, use the `custom_config` attributes namespace
to set the bucket name.

Closes #90
[FIX] Prevent Monit tenmplate failures on non-standard Monit books

The https://github.com/phlipper/chef-monit cookbook does not define
the `monitrc` method, but uses the `monit_monitrc` LWRP.

See phlipper/chef-monit@2802d1251a506d7553c8ebf91de1f734aa649199