MAGIC variance reduction

I added the MAGIC variance reduction technique to variancereduction.py. @makeclean, you should review the method. Tests were also added.

Theory manual addition still needed.

issue #344
Yes, so @elliottbiondo and I had this discussion at the hackathon about whether to do it globally or per e group. Our consensus was to do it per e group because that is what was done in the R2S implementation. So yes, given that there are two energy groups here, there will be 2 entries for 0.5.