v2019.7.21

• Add CubicSupercellTransformation and PerturbedSupercellsTransformation (@rees-c, @utf)
• Add interface for ShengBTE (@rees-c, @utf)
• Add interface for Vampire (@ncfrey)
• mproved Lobster interface (@JaGeo)
• Bug fixes (@sthartman, @dwinston, @utf)
• New functionality for calculation of Heisenberg exchange parameters (@ncfrey)
• Improvements to Miller indices handling and Lattice (@richardtran415)