Add responder object to intent listener

A responder object receives the string params from a message bus action and stores them in initialize
In a responder when params are parsed, they are stored
A responder parses params to a hash
When a responder is initialized parse the params

Refactor subject to be explicitly called responder for better test reading
Pending test for intent class name -- need channel
A responder is initialized with a channel
Intent class name returns a string of the class name
A responder has an intent class
Pending spec for apply in Responder until intent
Add intent object to responder
An intent object is memoized
A responder can apply its intent
A small integration test for responder
Refactor intent listener to use responder