Clean up Sinon cribs, Make Multifunction export more obvious

Thanks for being so responsive. I [ran the sinon chai examples past the maintainer](https://github.com/domenic/sinon-chai/issues/44) in domenic/sinon-chai#44 and he suggested some changes. I then incorporated one style that [might address the concerns] (https://github.com/JonJagger/cyber-dojo/issues/41) you raised here domenic/sinon-chai#44. Can you tell I'm learning github markdown? :smile: