fixes switching the playback  to 'stalled' state if any of buffers is empty
report invalid mpd
when stalling a buffer make sure that segments are scheduled so that it can be resumed eventually.
makes clickable only a non-transparent part of "Fork me on Github" ribbon
resolves a pending deferredInitAppend promise before it is reinitialized instead of rejecting it
fixes availabilityWindow calculations for SegmentTimeline
fix issue #131
suspends manifest updating when paused
fixes manifest rescheduling when paused
keeps currentTime inside availability window after pause
convert to more UI friendly buttons
Merge branch 'github-buttons' into development

Conflicts:
	index.html
Merge pull request #135 from nweber/development

Github buttons
adds initial TTML support
adds a verification that TTML document conforms to timing and structural constraints
fixes IndexSizeError when removing TextTrackCue's in TextTrackExtensions.deleteCues
resets textSourceBuffer when switching mpd's
ttml bugs fixes
handles ttml parsing errors
fixes structural constraints check