Combine all canPlayType tests into a single test framework

There is much more of canPlayType to be tested in later commits.
Add the missing types and codecs used in spec examples
Add the Opus codec, supported by at least Gecko and Chromium
Test that bogus codecs are not supported

Chrome and Safari fail this assertion.
Test fewer codec combinations with canPlayType
Add/remove types/codecs in the canPlayType test

Add audio/wav and VP9.

Remove codecs which are unlikely to ever be supported.
Use a single helper function t(type, expected)
Remove trailing argument copypasta
Merge pull request #690 from foolip/canPlayType

Merge and improve the canPlayType tests