Added MCNP interface for source sampling.
Changed tag names and mode indexing (MCNP idum numbers are indexed from 1).
Doc strings.
SG fixes
Made Fortran API non-specific for MCNP.
Starting documentation.
Adding doc file.
All code in documentation works.
Final Cleanup.
Removing source.F90
Added new source.F90
Merge pull request #512 from elliottbiondo/fortran

Fortran interface to Sampler class
collapse_element stub implemented; builds
Test stub implemented; passes nosetest
Identify comps to collapse
Pre-cleanup: passes nosetest
Mostly cleaned up; more testing to to do
More cleanup
Implement exception zlist; 20 lines -> 10 lines
Update header doc