Function to generate ALARA input blocks

This PR consists of a function to generate all the ALARA input blocks that are not generated by ```mesh_to_geom``` in order to create complete input files. The function only supports single pulse irradiation. 

This function may belong in the pyne/physor2014 repo instead of here. I am PRing at the request of @scopatz and @gidden, so that they and the community at large may decide if this is worthy. For me, the single pulse limitation might push this over the _ad hoc_ threshold of not belonging in a library. Perhaps others disagree. The API for fully supporting this would involve users supplying fairly tedious input. Maybe that's what we want, in which case I can implement this in the near future. For now, this will work for the PHYSOR paper.