Pull #1292, Fixing a missing quote mark - Accessibility slider control
improved screen reader accessibility of captions
Changed aria-live to assertive, thanks @joedolson.
Added role timer and aria-live off to prevent screen reader from constantly reading out time index
Pull #1292, Various fixes to accessibility enhancements to the slider

* Improve CSS style for ".mejs-offscreen" - prefer "top" for RTL languages.
* Make the text "Use Left/Right Arrow keys..." an option - so customized players can modify where and how they present this help text;
* Clarify JS comments - "Accessibility for slider" in place of "[sic] Ally for slider";
* Ensure "updateSlider()" Javascript function is called - to add WAI-ARIA attributes - role, aria-now, aria-min ...;
* (src/js/mep-player.js:282) - ensure "videoPlayerTitle" applies to audio players as well as video players;
Merge pull request #1270 from IET-OU/iet-ou/CR1262/a11y

Accept IETF language tags, plus accessible play/pause button -- "iet-ou/cr1262/a11y"
Merge pull request #1342 from IET-OU/allyProgress

Fix a missing quote mark in Javascript + various other fixes -  accessibility slider control [Pull #1292]
Merge pull request #1341 from rylan/a11yTime

Improve A11y of time feature.
Merge pull request #1340 from rylan/a11yTracks

Improved screen reader accessibility of captions
updates to updates
Speed cleanup
2.16.0 files
Updated log and tester
Strict checks skip check for `undefined`

This broke here:
https://github.com/johndyer/mediaelement/commit/9304e51fc52561acbf44341671796e919b5cbda3#diff-c828f76ddf61bb6b8160755ebf3de782R970

Ultimately, you want to not set the poster if the value of `posterUrl` is falsely. Previously, `undefined` didn't make it through because `undefined == null` equals `true` but `undefined === null` equals `false`. In the 2nd case, `posterUrl` is only checked for empty string and `null`, but the function call is derived from, `player.$media.attr('poster')`, returns `undefined`.
Merge pull request #1348 from staylor/patch-3

Strict checks skip check for `undefined`
Updating 2.16.1 changes
2.16.1
2.16.1