* Global configuration variables such as VASP_PSP_DIR and MAPI_KEY are now
stored in "~/.pmgrc.yaml". If you are setting these as environmental
variables right now, you can easily transition to the new system using::
pmg config --add VASP_PSP_DIR $VASP_PSP_DIR MAPI_KEY $MAPI_KEY
This new scheme will provide greater flexibility for user-defined
global behavior in pymatgen, e.g., tolerances, default input sets for
transmuters, etc., in future.
* Beta of k-point weight calculator.
* Use default MSONable as and from_dict for all transformations.