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
Formatting adjustments.
Simplify DuplicateRemoval code.
1. Remove usage of convex hull generator for computing chempot ranges. No more usage of convex_hull which uses -QJ option.
2. Implementation of multicomponent capability.
Merge branch 'master' into pourbaix
Merge branch 'pourbaix' of https://github.com/materialsproject/pymatgen into pourbaix