allow self_signed_ssl option

Following up [cf_swift_service#7](https://github.com/anynines/cf_swift_service/pull/7), I want to be able to pass in a `:self_signed_ssl` option in case I have swift setup with a self signed ssl certificate. The issue is further explained in [cf_swift_service#4](https://github.com/anynines/cf_swift_service/issues/4) by @rkoster and mentioned in #81.