Fix CursorIterator.next() for Python 3
Fix CursorIterator.next() for Python 3

It was calling next, but returning None

srimanthd/tweepy,vivek8943/tweepy,awangga/tweepy,rudraksh125/tweepy,yared-bezum/tweepy,zhenv5/tweepy,arunxarun/tweepy,techieshark/tweepy,thelostscientist/tweepy,damchilly/tweepy,tsablic/tweepy,vishnugonela/tweepy,cogniteev/tweepy,hackebrot/tweepy,LikeABird/tweepy,Choko256/tweepy,elijah513/tweepy,takeshineshiro/tweepy,conversocial/tweepy,raymondethan/tweepy,iamjakob/tweepy,truekonrads/tweepy,kskk02/tweepy,sa8/tweepy,kcompher/tweepy,edsu/tweepy,kylemanna/tweepy,atomicjets/tweepy,obskyr/tweepy,vikasgorur/tweepy,tuxos/tweepy,wjt/tweepy,aleczadikian/tweepy,robbiewoods05/tweepy,IsaacHaze/tweepy,sidewire/tweepy,bconnelly/tweepy,aganzha/tweepy,svven/tweepy,tweepy/tweepy