v2018.12.12

• Support for IUPAC ordering of elements in Composition formulae (@utf)
• Various bug fixes including returning integer miller indices, catching negative values in Composition and fixes to graph analysis (@utf), fix to Composition serialization (@jmmshen), defect analysis (@HanmeiTang), removing sites in surfaces (@yiming-xu), and fix to support the new PROCAR format in VASP (@dkorotin)
• PMG_MAPI_ENDPOINT environment variable added to support different endpoints for the Materials Project REST interface (@mkhorton)