Upgrade Sinon.JS to 1.17.3

Upgrade Sinon.JS to 1.17.3

No major changes for us other than a bugfix that makes the
following work as expected:

  var clock = this.sandbox.useFakeTimers();
  setTimeout(function () {
  	clock.tick(10);
  });
  click.tick(1);
  // Expected: 11ms is recorded
  // Actual: 1ms is record

This was broken up until Sinon 1.16.0 (Lolex 1.3.0) because it saved the
"clock.now" value before running any pending timeout callbacks. Then it
unconditionally assigned the "clock.now" value to 'oldNow + ticked', which
discarded ticks made by a callback.

Change-Id: I2775f4c6353aef12ced6dc45e73fe8d4e49c2b68