Stopped overriding the ping method provided by the 1.0 API

Ping didn't match the "castExists" regex so... Fixed the lack of castExists for ping/1.0 by removing
castExists all together from the API. It was the case anyway that all HEAD requests needed to be cast, so now the clientAction module will set that param when the spec is set to make HEAD requests. The transport.request still expects that parameter.

Switched the apiVersion implementation to use _.funcEnum, and exposed the options on the Client constructor. Docs to come.