Audio.js: jaws.Audio and its unit tests

Changes:
-- jaws.Audio! Finally, the introduction of an official jaws.Audio
object that uses jaws.assets to detect and load supported audio file
formats. (Currently checks for WAV, OGG, MP3, AAC, MKA, WEBA, and FLAC
support.)

-- Addition of tones{aac, flac, mka, mp3, ogg, wav} in test/assets for
testing Audio object in most modern browsers.

-- Unit tests for audio.js.

-- Commented out testing for text.js and quadtree.js in test/index.html
(new versions and testing to follow soon)