message: testing error when no url and adding an AudioBuffer
  additional test coverage
diff: @@ -117,6 +117,14 @@ define(["Test", "Tone/core/Buffers", "Tone/core/Buffer"], function (Test, Buffer
  });
  });
  + it("throws an error if no buffer exists with that name or index", function(){
  + var buffer = new Buffers();
  + expect(function(){
  + buffer.get("nope");
  + }).to.throw(Error);
  + buffer.dispose();
  + });
  +
  it("can add a Tone.Buffer", function(){
  var buff = new Buffer();
  var buffer = new Buffers();
  @@ -124,6 +132,15 @@ define(["Test", "Tone/core/Buffers", "Tone/core/Buffer"], function (Test, Buffer
  expect(buffer.get("name")).to.equal(buff);
  });
  + it("can add an AudioBuffer", function(done){
  + Buffer.load(testFile, function(buff){
  + var buffer = new Buffers();
  + buffer.add("name", buff);
  + expect(buffer.get("name").get()).to.equal(buff);
  + done();
  + })
  + });
  +
  it("can be constructed with Tone.Buffers", function(){
  var buff = new Buffer();
  var buffer = new Buffers({
  