2 small fixes: in NdArrayResolver and changeAttrExpression

Maybe it is also a good idea to add in DefaultResolver some logic for additional dictionary values evaluation in case of class has '\_\_getitem\_\_' method. 
I think doing the proposed change in DictResolver wouldn't work on some cases... consider the case where keys from dicts are custom user-made objects which override __eq__ and __hash__ (i.e.: you're going from a string which was passed to the client and resolving that key later on -- so, you really need to check for the id as it's possible you can't reconstruct the key object).