witbot.hears not a function

var Botkit = require('botkit')
var Witbot = require('witbot')

var slackToken = process.env.SLACK_TOKEN
var witToken = process.env.WIT_TOKEN

var controller = Botkit.slackbot({
  debug: false
})


controller.spawn({
  token: slackToken
}).startRTM(function(err, bot, payload){
  if (err){
    throw new Error('Error conntecting to slack: ', err)
  }
  console.log("Connected to slack")
})

var witbot = Witbot(witToken)

controller.hears('.*', 'direct_message,direct_mention', function(bot, message){
  witbot.process(message.text, bot, message)
})

witbot.hears('hello', 0.5, function(bot, message, outcome) {
  bot.reply(message, 'Hello to you as well!')
})