added the intern and first unit tests

I got intern running in-browser unit tests based on David Sprigg's [Esri Intern tutorial](https://github.com/DavidSpriggs/intern-tutorial-esri-jsapi).

I wrote one suite to test serializing image services. This pattern can be copied to test the other serialization methods.

I added instructions to README on how to install intern (`npm install`) and run the tests in a browser.