BUG : fixed _hdf_read_helper

Changed details of MD_dict underneath helper functions
BUG : fixed _iter_helper
ENH : sixified string test
ENH : add short-circuit for md_value input
BUG : sixified string test
INST : fixed setup.py

Fixed setup.py to reflect re-naming
TST : added test

First round of simple tests for MD_dict
BUG : fixed missing import in setup.py
BUG/ENH : fixed issues in reader/writer helper functions

scalar arrays now converted to python scalars.
TST : added round trip to hdf test
BUG : made py3k proof setup.py