Merge pull request #390 from mithro/test-expectations

Adding support for expected failure under some platforms.
Work around rAF timestamp being earlier than last seen performance.now() value.
Merge pull request #391 from shans/timingFix

Work around rAF timestamp being earlier than last seen performance.now()...
Merge pull request #392 from mithro/test-expectations

Add support for regex based matching of expected failures.
Making a firefox failure gating.
Adding test failure expectations for Firefox.