Updated readme with instructions on using JsTestCore.
Updated readme with instructions on using JsTestCore.

git-svn-id: 4b98d3960581bba9855fbc637fe3eb0eb4adbade@1522 af276e61-6b34-4dac-905b-574b5f35ef33

pivotalexperimental/js-test-core,pivotalexperimental/js-test-core,pivotalexperimental/js-test-server,pivotalexperimental/js-test-server