1.2.1

• Handle numberLiteral with numberLiteralExponent. See https://mathematica.stackexchange.com/questions/85445/convert-mathematica-math-expression-form-to-python-math-expression/226648?noredirect=1#comment576795_226648
• Add --debug, (-d) option to show pretty-printed AST (via astpretty)
• Add subscripting lists; this means we handle origin 1 vs.
  FoxySheep-1.2.1.tar.gz
  origin 0 indexing
• More tests