added doctests to esda/interaction
added doctests to esda/interaction
tectronics/pysal,tectronics/pysal,Alwnikrotikz/pysal,AlanZatarain/pysal,tectronics/pysal,AlanZatarain/pysal,Alwnikrotikz/pysal,Alwnikrotikz/pysal,AlanZatarain/pysal