Accept :hp_service_type option

In our setup, we need to be able to configure the option `hp_service_type`. This option already existed in fog for the hp service provider, which is used to setup the connection with swift. I submitted another [PR](https://github.com/fog/fog/pull/2177) to fog which makes this option overrideable.

This PR makes sure the option is passed through to the fog [connection] (https://github.com/anynines/cf_swift_service/blob/master/lib/swift_service/storage.rb#L24).

If merged, I will also make a PR for the cf_swift_service_release, enabling me to add the option to my bosh manifest.