I having been making assorted add ons for the Raspberry Pi for a while I am surprised that more Raspberry Pi Hats haven't been released. I think one of the main reasons is that people are sometime scared to develop on a platform that may not be as electronically robust as the Ardunio (but if you check your wires it should be just fin). The other reasons is the lack of tools that are already available. Most electrical design softwares actually come with an Ardunio shield as one of the main example files.
I think we need this for the Raspberry Pi. This project is hopefully the start of that. I want to make it easy for people to develop Hats for the Pi while also getting design feedback. So this is Rev0.1! I have used it on 4 different hats now and it has worked out great! So if you are interested fork the project on git and make something.