Reporter: Ensure markup is valid XHTML

Build: Ensure markup is valid XHTML (entities and empty elements)

Fixes #645
Tests: Increase max expected time for 'timing' test module

Android is too slow to meet the previously expected maximum time asserted

Should resolve the failure in http://swarm.jquery.org/result/2048943
Core: Implements QUnit.skip

Also logs skipped tests on testDone callback that are handled on the html reporter

Fixes #637
Fixes #434