Dev environment : closure compiler + jshint update

Fixed error raised by closure compiler
Added es3 option to jshint (detect trailing commas)
Added curly option to jshint (missing curly braces for if/for blocks)
Removed trailing whitespaces (not enforced through jshint though)

js/utils/Serializer.js

@@ -32,7 +32,7 @@
         var pData = data.piskel;
         var layers = pData.layers.map(function (serializedLayer) {
           return pskl.utils.Serializer.deserializeLayer(serializedLayer);
-        }); 
+        });
         var piskel = new pskl.model.Piskel(pData.width, pData.height, pData.fps);
         layers.forEach(function (layer) {
           piskel.addLayer(layer);