Remove leading underscore for procrustes_results

The string the code was checking was '_procrustes_results.txt' and there
are times where the filename is only 'procrustes_results.txt' causing a
problem when a file with that name was found.

Additional changes that took place in this commit:
    - Broke strings to make the description of --number_of_segments 80
      columns.
    - Remove some un-used imports from the interface.
    - Corrected the documentation for -b