remove multiple calls to setContext, do it in audiocontext

When we load tone.js modules we need to ensure that they run in the same audio context. Calling setContext multiple times results in multiple message handlers in the Tone worker node (a separate issue we should look into!)

Author: therewasaguy

src/audiocontext.js

@@ -1,8 +1,10 @@
 'use strict';
 
-define(['StartAudioContext'], function (require, StartAudioContext) {
+define(['StartAudioContext', 'Tone/core/Context', 'Tone/core/Tone'], function (require, StartAudioContext, Context, Tone) {
   // Create the Audio Context
-  var audiocontext = new window.AudioContext();
+  const audiocontext = new window.AudioContext();
+  Tone.context.dispose();
+  Tone.setContext(audiocontext);
 
   /**
    * <p>Returns the Audio Context for this sketch. Useful for users

src/envelope.js

@@ -8,9 +8,6 @@ define(function (require) {
   var Scale = require('Tone/signal/Scale');
   var TimelineSignal = require('Tone/signal/TimelineSignal');
 
-  var Tone = require('Tone/core/Tone');
-  Tone.setContext( p5sound.audiocontext);
-
   /**
    *  <p>Envelopes are pre-defined amplitude distribution over time.
    *  Typically, envelopes are used to control the output volume

src/master.js

@@ -1,12 +1,13 @@
 'use strict';
 
+const audiocontext = require('audiocontext');
+
 define(function () {
 
   /**
    * Master contains AudioContext and the master sound output.
    */
   var Master = function() {
-    var audiocontext = p5.prototype.getAudioContext();
     this.input = audiocontext.createGain();
     this.output = audiocontext.createGain();
 

src/signal.js

@@ -9,10 +9,6 @@ define(function (require) {
   var Mult = require('Tone/signal/Multiply');
   var Scale = require('Tone/signal/Scale');
 
-  var Tone = require('Tone/core/Tone');
-  var p5sound = require('master');
-  Tone.setContext( p5sound.audiocontext);
-
   /**
    *  <p>p5.Signal is a constant audio-rate signal used by p5.Oscillator
    *  and p5.Envelope for modulation math.</p>