function getEventNames(eventType, namespace) {
  const method = formatMethod(eventType)
  const postFix = (namespace) ? `:${namespace}` : ''
  // `typeStart:pluginName`
  const type = `${eventType}${postFix}`
  // `type:pluginName`
  const methodName = `${method}${postFix}`
  // `typeEnd:pluginName`
  const end = `${method}End${postFix}`
  return [ type, methodName, end ]
}
Return array of event names
@param  {String} eventType - original event type
@param  {String} namespace - optional namespace postfix
@return {array} - type, method, end