Fixed usage example

Hi Hendrik,

I hope you fine? It was nice meeting you in Hamburg.
I'm currently taking a deeper look into tent.io and your node implementations. Great stuff! Just wanted to say thanks for the short introduction and overview etc.

While I was playing around with your module I noticed a tiny bug in the example in the README.md - just wanted to let you know. Keep thinks up while I will try to catch up ;)

See you,
Thorsten