fixing nucid for openmc cross-sections
adding test for nucid fix
using nucname.mcnp_to_id instead of the more general nucname.id so our failures will be easier to debug in the future
fixing failure when zaid is 0
Merge pull request #633 from jdangerx/openmc-nucid-fix

Openmc nucid fix
Merge branch 'develop' of github.com:pyne/pyne into develop