Make PyScheduler more robust.
 Fix typos
 Refactoting PyFlowScheduler.
 Use **kwargs interface for PyFlowScheduler.
 Force scheduler shutdown if self._callback raises an exception
 Add flow status to mail subject.
 New format for the mail sent by FlowScheduler.
Merge branch 'master' of https://github.com/gmatteo/pymatgen

Conflicts:
	pymatgen/io/abinitio/launcher.py
Merge branch 'master' of https://github.com/yanikou19/pymatgen

Conflicts:
	pymatgen/io/abinitio/tasks.py