fixing alpha 0 closes #285

Author: lauren mccarthy

lib/p5.js

@@ -1,4 +1,4 @@
-/*! p5.js v0.2.23 August 04, 2014 */
+/*! p5.js v0.2.23 August 05, 2014 */
 var shim = function (require) {
     window.requestDraw = function () {
       return window.requestAnimationFrame || window.webkitRequestAnimationFrame || window.mozRequestAnimationFrame || window.oRequestAnimationFrame || window.msRequestAnimationFrame || function (callback, element) {
@@ -464,7 +464,7 @@ var p5Color = function (require, core, constants) {
       for (var i = 0; i < 3; i++) {
         a[i] = Math.floor(a[i]);
       }
-      var alpha = a[3] ? a[3] / 255 : 1;
+      var alpha = typeof a[3] !== 'undefined' ? a[3] / 255 : 1;
       return 'rgba(' + a[0] + ',' + a[1] + ',' + a[2] + ',' + alpha + ')';
     };
     p5.Color.getColor = function () {