Add "real" README

[keimlink]

The README is currently the first page of the book. But in my opinion it would be better if the README would explain the purpose of the project and how to create, edit and contribute to it.

For example it is not obvious for someone who has no experience with gitbook how to install it and serve the book locally.

[olasitarska]

Yeah, I think gitbook treats the main README.md file as a first chapter, so I don't know if there is a way to update this README.md without chaning the introduction chapter on gitbook. We will figure it out later this week :)

[miohtama]

Apparently Gitbook does not support overriding README.md.

My suggestion is to add CONTRIBUTING.md which explains

• Link CONTRIBUTING.md to the bottom of README.md
• What is this project
• Who is maintaining it
• What is the edit workflow (and toolset) if you want to publish fixes to the documentation

[oinopion]

Fixed by #45.