Update README.md

[Aku-n06]

Usually the #pragma mark has a "-", to make the description easier to read.
Maybe I'm wrong, but I've always seen only this format of #pragma mark

[soberman]

There are two styles - with and without -. They both give you different results. Just try both of them and see for yourself in your Xcode.

[joshaber]

Indeed. This guide is mostly descriptive of how we style our code, and we generally don't use the -.

Thanks for opening this though!

[Aku-n06]

Ok, thanks for your clarification.