removed N/A and replaced with Not Supported

As discussed on the mailing list, tests will be marked by evaluators as
"supported" or "not supported"; there is no longer an N/A option.
added skippability and escapability tests, including SMIL but without audio (note: OPF duration metadata is set at 1s, until we include proper audio files)
use a different escapability name, as sidebar is also skippable
embedded media test (auncherOSX passes)
test for phrase-level navigation (audio previous/next granularity sentence/word/paragraph, etc.)
granularity fixes
added video embedded
playback active class test
Merge pull request #47 from mgylling/remove-NA

Remove N/A and replace with Not Supported