Minor Py3k modernization.
Improvement to composition using sets.
Merge remote-tracking branch 'mpmaster/master'
Revert "Minor Py3k modernization."

This reverts commit 1439c510a8b8e58b3cad9a0a902be49e38aa0928.
Merge remote-tracking branch 'mpmaster/master'
Modernize borg.
fix ghost atom output parsing
Merge remote-tracking branch 'origin/master'
Use mock for testing VTK.
Merge branch 'master' of github.com:materialsproject/pymatgen
Disable vtk test for now.
Add git pull.
Merge remote-tracking branch 'mpmaster/master'
Add flow.to_dict, as_dict, from_dict