Check startTime of cues is lower than endTime
Created by: epiclabsDASH
Fix #2202 (closed)
In Edge browser, whenever a TextTrackCue object has an startTime greater than its endTime, an exception is raised avoiding all the other parsed cues to be shown.
Note: Although this issue is raising an issue within captions provided by the user (external or fragmented using wrong startTime/endTime values), we need to make dash.js resilience against this kind of situations. So, this PR.