Update babylon.engine.js

Babylon/babylon.engine.js

@@ -576,7 +576,7 @@ var BABYLON;
         });
         Object.defineProperty(Engine, "Version", {
             get: function () {
-                return "2.1.0 alpha";
+                return "2.1.0 beta";
             },
             enumerable: true,
             configurable: true
@@ -1898,4 +1898,4 @@ var BABYLON;
     BABYLON.Engine = Engine;
 })(BABYLON || (BABYLON = {}));
 
-//# sourceMappingURL=babylon.engine.js.map
+//# sourceMappingURL=babylon.engine.js.map