v0.3.0

• new options to combine spins in one plot:
  • --mix-spins adds the characters together to draw a single set
    of lines, forcing the energies to be equal for both spins
    (may be better for antiferromagnetism)
  • --join-spins draws separate lines for each spin in one plot
    (more appropriate for ferromagnetism)
• new options --out-suffix, --config-file, --verbose
• change delimiter for combined atoms/orbitals to ++ (or &) to
  avoid clash with orbital names that contain +
• make atoms and orbitals case insensitive
• colors may be also given in HTML-style hex notation or color names;
  and may be prefixed by a factor, for scaling (F × COLOR)
• read Fermi energy from case.scf rather than case.scf2; do not
  require it unless needed