back to ruby 2.1 while I see what breaks in 2.2
back to ruby 2.1 while I see what breaks in 2.2

fabien-michel/closure_tree,froderik/closure_tree,procore/closure_tree,mceachen/closure_tree,procore/closure_tree,froderik/closure_tree,seuros/closure_tree,seuros/closure_tree,froderik/closure_tree,procore/closure_tree,mceachen/closure_tree,mceachen/closure_tree,fabien-michel/closure_tree,fabien-michel/closure_tree,seuros/closure_tree