Use new AudioContext() rather than webkit

It is my opinion that we ought to author according to W3C's latest
drafts rather than continue to cater to webkit's unique (non-standard)
implementation.

Please consider -- and thanks for writing such nice code!

abbey-load.js

@@ -6,7 +6,7 @@
 (function (window, undefined) {
     var filesLoaded = 0,
         numberOfFiles = 0,
-        context = new webkitAudioContext(),
+        context = new AudioContext(),
         buffers = [];
 
     var AbbeyLoad = function (files, callback) {