add comments in dao#build code

lib/dao-factory.js

@@ -154,10 +154,12 @@ module.exports = (function() {
     instance.__factory = this
 
     Utils._.map(this.attributes, function(definition, name) {
+      //transform integer 0,1 into boolean
       if(definition.indexOf(DataTypes.BOOLEAN) !== -1 && typeof instance[name] === "number") {
         instance[name] = (instance[name] === 0) ? false : true;
       }
 
+      //add default attributes
       if(typeof instance[name] == 'undefined') {
         var value = null