Overwrite HTML5Video inherited methods

[joaopaulovieira]

Summary

This PR updates seek and pause methods to overwrite HTML5Video Class inherits.

Changes

• Set the current time on video element when the seek(time) method is called;
• Call videoElement.pause method when pause plugin method is called;

How to test

All changes in this PR should not impact any use of the DashShakaPlayback.

[leandromoreira]

LGTM but just out of curiosity, why?

[joaopaulovieira]

@leandromoreira In the latest version of clappr-core, we add behaviors in these inherit methods via HTML5Video that probably cause problems if one playback call super and do other operations.

So, to avoid one bigger refactoring, we can just stop calling super and do the operation on the video element directly on playback implementation.