added doc links to bodrov's sitepoint tutorial and a thank-you to the contributing devs
added doc links to bodrov's sitepoint tutorial and a thank-you to the contributing devs

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