Index refactor

working on a refactor if the Index class to no longer inherit from ndarray.

Their is something missing here as all of the json stuff give:

``ValueError: 'Label array sizes do not match corresponding data shape``

I am prob just missing some ndarray compat function/property...can you have a look?

commits start here: 
https://github.com/jreback/pandas/commit/09daf4ab941f08ee9baea24b5758ffdfa616a8bd