Redesign auto-generated ALARA flux information to correspond to new interval information

[gonuke]

Since the spatial intervals will now be generated as 1 per cell fraction (#62), the flux information needs to be generated in the same fashion and order to be consistent.

This should be a modification to scripts/r2s/io/write_alara_fluxin.py:

• for each mesh voxel
  • query the number of cell volumes, C
  • write the flux for that voxel C times