Pymatgen

* Bug-fix for missing HHI data file.
* Misc bug fixes.

* Dash docs now available for pymatgen. See pymatgen.org "Offline docs" section
for details.
* Better CrystalNN. (Anubhav Jain)
* Fixes for elastic module. (Joseph Montoya)

* Improvements to qchem (samblau).
* Improvements to nwchem to support tddft input and parsing (shyuep).
* Improvements to CrystalNN (computron).
* Add methods for getting phonon BS, DOS, and DDB output (dwinston).

* Neutron diffraciton calculator (Yuta)
* Non-existent electronegativity (e.g., He and Ne) are now returned as NaN
instead of infinity.
* CifParser now handles Elements that are in all caps, which is found in some
databases. (Gpretto)
* Improvements to local_env (Anubhav Jain)
* Improvements to Qchem ()
* Inputs sets for NMR (Shyam)
* New ChargeDensityAnalyzer class to find interstitial sites from charge density (Hanmei)

* Updated Debye temperature formulation (Joey Montoya)
* Add bandgap option for FermiDos for scissoring (Alireza Faghaninia)
* Improved Pourbaix code (Joey Montoya)
* Local env code improvements (Nils)

* Bug fixes to structure, phase diagram module, enumlib adaptor, local env analysis.