feat(result.duration): report test duration in ms

Wrap spec start/complete in Timer start/elapsed.
configuration.timeSpecDuration = false will disable feature.

 * Add Suite result.duration, elapsed time in ms

 * Remove timeSpecDuration option.

 * Respond to review, use noopTimer

spec/core/integration/EnvSpec.js

@@ -1436,6 +1436,9 @@ describe("Env integration", function() {
         status: 'pending'
       }));
 
+      var suiteDone = reporter.suiteDone.calls.argsFor(0)[0];
+      expect(typeof suiteDone.duration).toBe('number');
+
       var suiteResult = reporter.suiteStarted.calls.argsFor(0)[0];
       expect(suiteResult.description).toEqual("A Suite");