lib/off.js
function off (state, eventName, handler) {
  if (arguments.length === 2) {
    state.emitter.removeAllListeners(eventName)
  } else {
    state.emitter.removeListener(eventName, handler)
  }

  return state.api
}
function off (state, eventName, handler) {
  if (arguments.length === 2) {
    state.emitter.removeAllListeners(eventName)
  } else {
    state.emitter.removeListener(eventName, handler)
  }

  return state.api
}
function off ( state , eventName , handler ) { if ( arguments . length === 2 ) { state . emitter . removeAllListeners ( eventName ) } else { state . emitter . removeListener ( eventName , handler ) } return state . api }
unbinds event from handler

@param  {String} eventName   push, pull, connect, disconnect
@param  {Function} handler   function unbound from event
@return {Promise}
unbinds event from handler