ENH : first pass at MD_dict to handle nested mete-data

 - can get/set by dotted paths
 - can read/write to hdf groups in compliance with DataExchange
ENH : add json_entry to ArgSpec classes

Dumps the data to a dictionary for use with json
ENH : scaled back tool class

Stripped out json generation code
ENH : first pass at handle registry

decorator which sub-classes the decorated class from each of the
interfaces given.
ORG : renamed folder
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
TST : adding travis config
DOC : added travis tag to README
DOC : README tweaks
removed InterfaceRegistry

new-style objects already keep track of subclasses (via
`baseKlass.__subclasses__()`).