Make sure we remove all document listeners on dispose.

[mynameisstephen]

The slider is not removing document event listeners on dispose. I have a feeling that there are other instances within other components.

[heff]

The document listeners are removed on the slider's mouseup event, so this would fix the case that the player is disposed of in the middle of sliding a slider. Seems unlikely but not impossible. Was there a specific use case where you saw this happen, or are you finding the listeners aren't being removed on mouseup as expected? Or is this tightening things up?

[mynameisstephen]

Essentially I have a rudimentary playlist which plays a video and on complete disposes the video player and creates a new one with the next video. I get a null error when seeking to the end of the video causing it to trigger the complete event and than dispose the video player.

TypeError: element is null

vjs.removeClass@http://dev.local/static/js/video.dev.js:996:1
vjs.Component.prototype.removeClass@http://dev.local/static/js/video.dev.js:2288:3
vjs.Slider.prototype.onMouseUp@http://dev.local/static/js/video.dev.js:2749:3
vjs.SeekBar.prototype.onMouseUp@http://dev.local/static/js/video.dev.js:5232:3
vjs.bind/ret@http://dev.local/static/js/video.dev.js:868:5
vjs.on/data.dispatcher@http://dev.local/static/js/video.dev.js:343:13

#1476 is another example of event listeners staying alive. Disposing a video player while in full screen mode eventually causes a null exception.

[heff]

This one is pretty simple so I'll pull it in for the next release. Ideally we'll move towards what's described in #1544 to handle this situation.

[heff]

Merged in. Thank you!