A simple spy/stub for when you need to stub chainable calls.
I wrote this because I was writing some tests for an angular class that had a declaration
this.d3 = d3.getService() and I was trying to test around the d3 stuff. This just allows you to stub something chainable so you can work with the rest of your code.
Use: See the index.spec.js. ChainableStub.__spies.whatever will return a Sinon spy (http://sinonjs.org)