Pymatgen

* Massive cleanup to Boltztrap interface (Anubhav Jain)
* Refactor of piezoelectric analysis to use tensor base class (Joey)
* More robust CIF parsing.

* Pymatgen now uses spglib directly from Togo's website. Spglib is no longer
bundled as a dependency.
* Improved support for velocities in Poscar (Germaine Vallverdu)
* Backwards incompatible change in Born charge format in Outcar.
* Fixes for Lammps input serialization

* Misc refactorings and bug fixes, especially for Outcar and Boltztrap classes.

* Minor update to DerivedInputSet interface.

* New derived input sets for generating inputs that depende on previuos
calculations. Old input sets deprecated.

* Chemical environment analysis package (David Waroquiers).
* Piezoelectric property analysis (Shayam).
* Cythonize certain expensive core functions. 5-10x speedup in large structure matching (Will Richards).
* New NMR parsing functionality for Outcar (Xiaohui Qu).
* Improved io.lammps (Kiran Mathews).
* Update to spglib 1.9.2.
* Element properties now return unitized float where possible.
* Bug fix for get_primitive_standard affecting rhombohedral cells (important for band structures).
* Vasprun.final_energy now returns corrected energy with warning if it is different from final electronic step.