minor
Add failing tests
Make indexes to compile. This fix test2 and test4. test3 still fails probably because another issue.
minor
Change class name
Add another overload to GroupBy method, which will wrap the grouped object with out own, in order to solve an issue with the Looked,Grouped object been internal.
The TransformGroupByExtensionMethodTransformer class is not needed but is added for reference only.
Add a nice util method to assert no index errors