test: Update qunitjs to v1.14.0

Code:
 https://code.jquery.com/qunit/qunit-1.14.0.css
 https://code.jquery.com/qunit/qunit-1.14.0.js

Release notes:
 https://github.com/jquery/qunit/blob/v1.14.0/History.md

Change-Id: If60b4d36805150707ef5646030fcd4f788a9da85
build: Use .txt extension for intro.js and outro.js

Change-Id: Ie4cc45de05d88efa23387a2501d1cc1ae5bfdfd5