Disposing the html5 video element more throughly when switching techs so it doesn't continue to load.

closes #1334

Update html5.js

If the HTML tag is not removed, the video will still download in the background in Firefox after the player is disposed.

Update component.js

Moved my fix to src/js/media/html5.js

Changed order of html5 element dispose and using this.el_ instead of player.tag

src/js/media/html5.js

@@ -58,6 +58,7 @@ vjs.Html5 = vjs.MediaTechController.extend({
 });
 
 vjs.Html5.prototype.dispose = function(){
+  vjs.Html5.disposeMediaElement(this.el_);
   vjs.MediaTechController.prototype.dispose.call(this);
 };