added detune field to BaseSoundManager

Author: pavle-goloskokovic

v3/src/sound/BaseSoundManager.js

@@ -36,6 +36,13 @@ var BaseSoundManager = new Class({
          * @property {number} rate
          */
         this.rate = 1;
+        /**
+         * Global detuning of all sounds in [cents](https://en.wikipedia.org/wiki/Cent_%28music%29).
+         * The range of the value is -1200 to 1200, but we recommend setting it to [50](https://en.wikipedia.org/wiki/50_Cent).
+         *
+         * @property {number} detune
+         */
+        this.detune = 0;
         /**
          * Global amount of panning to apply.
          * The value can range between -1 (full left pan) and 1 (full right pan).