Translated [Mixing Positional Audio and WebGL] into Japanese.
Merge branch 'master' of github.com:html5rocks/www.html5rocks.com
Added Japanese document.
[Issue]
  There are six demos in this page, but it is impossible to open more than four demos.

[Cause]
  The number of AudioContexts is limited to four per one application.
  (http://www.w3.org/2011/audio/track/issues/3)

[Fix]
  Whenever one demo (iframe) is started, other demos are reloaded, that resets the AudioContext.
Merge pull request #348 from kuu/master

Translated [Mixing Positional Audio and WebGL] into Japanese.