add a method in BandStructure to get the direct band gap
add an option in RemoveDuplicatesFilter to also us symmetry in addition to the structure matcher
fix a small bug in SubstitutionTransformation. Sometimes the string method broke because it could not concatenate an object and a string
fix a few small bugs in substitutor and give the option to use symmetry to remove duplicates in addition to the matcher
Merge branch 'master' of github.com:materialsproject/pymatgen

Conflicts:
	pymatgen/alchemy/filters.py