Add option to suppress blank lines between sections

Not sure if you want this, but I use it locally :) Implemented such that the default is that spaces are inserted, and it is stored in the negative ("no blank lines between sections") so that the default for existing users is the current behavior (on, put blank lines between sections). I've only been doing xcode/objective-c for about 2 days, so sorry if I've mucked things up :-/ I'm not sure I really understand the .xib changes either, or else I'd try to clean that up by hand.

Let me know if you want this, or want me to make some changes before sending another pull request. Feel free to just tell me to buzz off :)