Add onCall(n) and friends to SinonStub definition

These were added in Sinon 1.8, and the definition claims to be Sinon
1.8.1

From documentation:
"As of Sinon version 1.8, you can use the onCall method to make a stub
respond differently on consecutive calls."

http://sinonjs.org/docs/
verified from src https://github.com/angular-ui/ui-router/blob/master/release/angular-ui-router.js

![image](https://cloud.githubusercontent.com/assets/874898/3347732/22bc0920-f8f6-11e3-8a8f-0ef29073264c.png)