Update setup.py

Adding a line of `description` would show a short description on pypi for search results instead of the default `UNKNOWN`
ENH Make figures look better in B&W.
FIX AddEvidence was not returning a value in some cases, giving compilation errors in Windows.
Merge branch 'master' of https://github.com/andre-martins/AD3
ENH Implemented MPLP.
FIX Corrected some minor issues in the notebook grid example.
MRG Some differences in Ising example.
ENH Implemented MPLP.
ENH A Python notebook for a simple coreference example.