Merge and expand audio_004.htm and video_001.htm

The existing tests only test that the playing event is fired, also test
that for the other three events fired in the same section of the spec.

This revealed a bug in Blink/WebKit, where canplaythrough is fired before
play and playing.
Verify readyState and paused state when autoplaying

Simplify the title to just autoplay since the test is quite general now.
Skip appendChild (media elements need not be in a document to autoplay)
Merge pull request #636 from foolip/autoplay

Merge and expand audio_004.htm and video_001.htm