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. 
This code to handle numpy arrays still won't work properly with non 1d arrays.

See a screenshot with the issue:

![pycharm_debugger2](https://cloud.githubusercontent.com/assets/117621/4122401/0272d09c-32c4-11e4-81b6-0eb4b1e630b3.png)

You should consider the obj.shape to create the accessors you want to resolve later on... You can possibly create a custom class to be a view of the part of the array you want in numpy and create a resolver for it.

Also, you probably want to do str(obj) only once and not multiple times (although numpy itself should be smart enough to trim it).