Add botan.io analytics

[Luchanso]

Bot analytics from issue #34 All tested on my bots

How to use:

var bot = new Bot({
  token: 'TOKEN HERE'
})
.enableAnalytics(botan_api_key)
.on('message', function (message) {
  console.log(message);
})
.start();

[shernshiou]

@Luchanso thanks.