Nested objects as default

Nested objects as default should not be overwritten by children types:

var Parent = Construct.extend({
      defaults: {
         obj: {
            foo: "Bar"
         }
     }
},{});

var Child = Parent.extend({
      defaults: {
         obj: {
             foo: "Baz"
        }
     }
}, {});

Parent.defaults.obj.foo should not be changed to Baz

See #65