Fix broken link in CONTRIBUTING.md

The link titled "Build and share plugins" goes to docs/plugins.md, which
doesn't exist. It should go to docs/guides/plugins.md
Merge pull request #1489 from walsh9/feature/doc-link-fix

Fix broken link in CONTRIBUTING.md
fixes #1512, fixes #1507

On ended, pause player if not paused or looping
IE11 (and maybe other browsers as well) only fire 'ended' event when the
video ends and doesn't fire pause. This makes IE11 not reset it's state
into a paused state that allows a user to replay immediately. However, a
two clicks on the play/pause button will allow you to replay.
In Chrome, we get first a pause event and then an ended event. When
'loop' is set, neither the last pause nor ended fire.
In the flash tech, the pause and ended events fire like in chrome in all
browsers.

Add tests for onEnded change

Appease jshint.
Added line to the changelog for #1512
Release 4.8.2
Merge branch 'stable'

Conflicts:
	dist/video-js/video-js.css
	dist/video-js/video-js.min.css
	dist/video-js/video.dev.js
	dist/video-js/video.js
Updated contrib.json to comply with new contrib formatting
Updated contrib.json to match new prompt formatting
Changed the MenuItem and the Volume Control bar to gain focus when using tab navigation.
Previously, they could not be navigated to via the keyboard.
Fixs #1517.
Tested via manaul cross-browser tests using keyboard navigation (chrome, firefox, safari, and IE 11 ).
@deedos added a Brazilian Portuguese translation. closes #1520
Updated to version 4.4.4 of the swf
Added line to the changelog for #1526
Release 4.8.3
Removed dist files
reverted the submenu behavior. it now needs to activated before it menuitems become tab targets. The volume control bar now uses the vjs-lock-showing class instead of new class.
Updated contrib.json to comply with new contrib formatting
Updated contrib.json to match new prompt formatting
@gkatsev fixed isFullscreen reporting on iOS devices. closes #1511

Squashed commit of the following:

commit 02fe7a40d0958e2ed84a6a0cf2be43bec259c72c
Author: Gary Katsevman <git@gkatsev.com>
Date:   Tue Sep 23 14:15:08 2014 -0400

    Feature detect old fullscreen instead of UA switch

commit f3eccbbe678c163021d790c69c3ab365e0a1fe1a
Author: Gary Katsevman <git@gkatsev.com>
Date:   Mon Sep 22 21:31:34 2014 -0400

    No need for if since assume we're in fs

commit 0498b100843e0aa858b166d02a467e4471c126ab
Author: Gary Katsevman <git@gkatsev.com>
Date:   Mon Sep 22 21:28:10 2014 -0400

    Revert "Don't trigget vjs's fullscreenchange event"

    This reverts commit cc45177ee5fa950e665e066d170b137aaeb6e398.

    Conflicts:
    	src/js/media/html5.js

commit 1ed30853efb2ea043da4f18b4fdf75da15f55e88
Author: Gary Katsevman <git@gkatsev.com>
Date:   Wed Sep 17 12:00:29 2014 -0400

    Listen via 'this.one'.
    Don't bother checking whether the video element is fullscreen but just
    assume we are fullscreen.

commit 27e27075083d2ad408b5d47055881b2554f59154
Author: Gary Katsevman <git@gkatsev.com>
Date:   Tue Sep 16 18:12:36 2014 -0400

    Use one for event binding.

commit cc45177ee5fa950e665e066d170b137aaeb6e398
Author: Gary Katsevman <git@gkatsev.com>
Date:   Mon Sep 15 17:28:46 2014 -0400

    Don't trigget vjs's fullscreenchange event
    This event isn't really being used for this usecase right now, so, no
    need to trigger it.

commit ad505a680785d638289657aec4edad60879e945a
Author: Gary Katsevman <git@gkatsev.com>
Date:   Mon Sep 15 16:45:48 2014 -0400

    Update exports for request & cancel fullscreen

commit e423635b6c8ad58a1ba04e1534a51c075e08b73a
Author: Gary Katsevman <git@gkatsev.com>
Date:   Mon Sep 15 16:15:10 2014 -0400

    On iOS, use ios specific enterFullscreen methods.

commit fe4a8fbf6ad73b6bc8f57d16c44f0ca4d3bf9450
Author: Gary Katsevman <git@gkatsev.com>
Date:   Mon Sep 15 14:53:20 2014 -0400

    Export isFullScreen correctly. Export isFullscreen as well.
Release 4.8.4
Merge branch 'stable'

Conflicts:
	dist/video-js/video-js.css
	dist/video-js/video-js.min.css
	dist/video-js/video.dev.js
	dist/video-js/video.js