Adding a test which makes sure there are no page errors.
Fixing the two borked tests.
Removing change-playback-rate-html
Merge pull request #257 from mithro/testharness-error-fix

testharness no longer ignores page errors (plus fixing tests which were actually borked)
Fixing update-testcases and run-tests to play nice together.
Make travis fail if testcases.jsonp is out of date.
Cleaning up pep8 found errors.
Removing disable-testcases.jsonp
Fixing typo in name.