Fixing type 'finaly' to 'finally'

I also reviewed the rest of the repository. Seems like some of your commits have made it more in line with what I had been thinking before. Specifically, moving the logic for `then`s, etc, out of the Enum status. It still seems to me that it'd be best to have a class per file (remove Deferred from Promise), but I'm not sure how the whole importing stuff works for that. Also, does Deferred extend Promise? I'm not super familiar with the syntax yet, but it seemed that way. If so, should it? Seems a bit strange that it would. 

Sorry for the extra space changes in the commit, apparently Xcode formatted the file while I had it open, and I didn't notice while committing.