Add pickle test for structures. Remove singleton decorator for PT.
Fix pickling for periodictable.
Revert "Fix pickling for periodictable."

This reverts commit a8df86f9ab23f4b8df297e5dc58ef86f5b61381a.
Fix Pickle Test.
Pull changes from stable_py3.
Increment monty req. Refactor to use monty.functools.lazy_property.
Merge branch 'master' into stable_py3

Conflicts:
	pymatgen/io/abinitio/tests/test_flows.py
	requirements.txt
	setup.py