Extract Connector classes to its own gem

Implementing @jtimberman's suggestion in https://github.com/RiotGames/ridley/issues/225.

This is still :construction:, because there my be some various things that still need to be removed / fixed.

See https://github.com/RiotGames/ridley-connectors and https://github.com/RiotGames/ridley-connectors/pull/1 for where this code moved and what is left to do on that side.