Add code mirror to test typings.

test/src/notebook/typings.d.ts

@@ -1,3 +1,4 @@
+/// <reference path="../../../typings/codemirror/codemirror.d.ts"/>
 /// <reference path="../../../typings/expect.js/expect.js.d.ts"/>
 /// <reference path="../../../typings/mocha/mocha.d.ts"/>
 /// <reference path="../../../typings/es6-promise/es6-promise.d.ts"/>