Added ParentDict class. Setting items in parent dictionaries of parameter and node (eg, to change value of constant parents for some reason) is now safe.
Added ParentDict class. Setting items in parent dictionaries of parameter and node (eg, to change value of constant parents for some reason) is now safe.

git-svn-id: 78c04ade7a39d415e1dfbdfb93d0db9e927fa022@253 15d7aa0b-6f1a-0410-991a-d59f85d14984

jameshensman/pymc3,kyleam/pymc3,MichielCottaar/pymc3,wanderer2/pymc3,arunlodhi/pymc3,MCGallaspy/pymc3,evidation-health/pymc3,LoLab-VU/pymc,wanderer2/pymc3,kmather73/pymc3,tyarkoni/pymc3,CVML/pymc3,clk8908/pymc3,arunlodhi/pymc3,clk8908/pymc3,evidation-health/pymc3,hothHowler/pymc3,LoLab-VU/pymc,superbobry/pymc3,JesseLivezey/pymc3,MichielCottaar/pymc3,tyarkoni/pymc3,dhiapet/PyMC3,hothHowler/pymc3,Anjum48/pymc3,superbobry/pymc3,jameshensman/pymc3,dhiapet/PyMC3,kyleam/pymc3,kmather73/pymc3,CVML/pymc3,MCGallaspy/pymc3,Anjum48/pymc3,JesseLivezey/pymc3