Contributing guidelines possibly outdated

Created by: hunkjazz

Hey, guys?!

I was wondering whether the contributing guidelines is outdated, especially in the "Pull Requests" section. When it mentions master, isn't it supposed to be v4-dev?

I tried to follow the steps using master at first, but I would have to fix lots of conflicts. So, I decided to use v4-dev instead, had no conflicts problems and an accepted PR.

If so, it would be misleading some developers. Right?!