
outstanding items (in no particular order):

* code clean up (e.g. ugly @A, @B, @D stuff)
* more flixable formatting (whitespace, number format,num_atoms, etc)
* support (test if ok as-is) for format supporting different atom names (e.g. He) and Z's
* smarter file_is()
* error-checking anywhere...
* tests!
* docs (esp options and supported format)
* add a 'no_build' option to skip build_zmat() call

