Changed setSource to add media element to root widget rather than body
Clean up tests a little
Added extra asserts to a test, which revealed a bug

Bug fixed by modifying configureSeekToFail() helper to reassign
the new 'seek' stub to seekSpy global. This is required by
deviceMockingHooks.finishBuffering().
Bolster other tests in the same way as previous commit

Add more assertions to ensure that something really happens on the
first run through the sentinels, as well as the second name (not
exclusively).
Tidied up the tests a bit
Merge pull request #197 from fmtvp/new-media-api-media-container

Changed setSource to add media element to root widget rather than body
Seek sentinel attempt count should be set to 0 in playFrom. Setting it to 0 in setSentinels will cause the undesired effect of a transition to buffering resetting the attempt count.

If a sentinel fails, it should allow any other sentinels to take their respective actions
Bolster HTML5 tests to ensure second sentinel retries when first has failed

(Based on an improvement we found we needed to make in CEHTML - see previous commit)
Added test to ensure seek sentinel attempt count is reset

Tweaked the equivalent test in HTML5 to enter buffering on playFrom()
and then exit it properly, rather than simply remaining in the PLAYING state
as we were inadvertantly doing before.
Merge branch 'master' into new-media-api-sentinel-limits