Implement Twitch Chat Whisper Functionality

[CryZe]

This is super cool: http://blog.twitch.tv/2015/06/whisper/
With this the bot can just write the Score to everyone instead of Top 5 or whatever it currently is. Also normal chat commands and / or replies could be private too I guess.

[Gyoo]

I'm still down to show the best scores to everyone but several commands will definitely be moved to whispers. I can see some good improvements to make the global chat less cluttered by SplitsBet this way.

We could also add a confirmation that the bet has been registered !