Read the paper and see what you think. Besides rekindling my interest in that movie, the article (which I think was written in an American setting by a foreign student for, whether British or French, I don't know) also put a little fire under my heinie to see more of Scorcese's heady oeuvre.
 That's right: I just tried again to neologize. Shan't is standard albeit somewhat more anachronistic English and means "shall not." Ain't is "incorrect" but totally intelligible (i.e., correct!) English, one of my favorite turns of speech and means am/are and has/have not -- in the latter case "hain't" being even sweeter. "Shain't" is just a fusion of shan't and ain't, "shall ain't". To be fair, there is folk precedence for "shain't"; however, whether that's based on dialect or actually means what I mean by shain't, I ain't too sure.