v2020.7.3

• Make Slabs properly serializable in as_dict. Fixes #1892.
• Fixes for Critic2Caller (@yuuukuma)
• Add cost data for He, H, Ar, Ne, Kr, Tc (@computron)
• Parse scientific notation in OUTCAR (possibly without spaces in between)
• Spin support for boltztrap2 (@fraricci)
• New static method to generate basis functions Lobster (@JaGeo)
• SLME and spillage analysis (@knc6)