added util to copy prototype methods
added util to copy prototype methods

cjohansen/Sinon.JS,mroderick/Sinon.JS,mroderick/Sinon.JS,fatso83/Sinon.JS,cjohansen/Sinon.JS,cjohansen/Sinon.JS,fatso83/Sinon.JS,mroderick/Sinon.JS,fatso83/Sinon.JS