Minor mod to accomodate neutral.txt change.
transitions.sh now outputs spin, nelec.

pynex.py now requires more input variables, transitions.sh
has been modified to extract them from the same starting files
and generatethe necessary input files.
Modification to lowest transition calculation.

Extensive changes to how the lowest state is calculated based
on the real hole charge spin difference. Also, nelectrons
is no longer read from .bands and must be supplied prior
to init (as with hole_charge). This is because CASTEP doesn't
report the true spin populations in the .bands file.
Changes to include spin read and nelectron init.

See changes in libpytep.f90 to explain what is going on
here. Basically, pynex now calculates the spin difference
and hole charge spin differences to figure out the
proper populations which are provided to libpytep in the init.