Add notice about README.md and CONTRIBUTING.md.

To ease understanding and cross team contributions, every repo should have a README.md and CONTRIBUTING.md. I have chosen to not go into specifics of what these should contain, as I believe that is rather self explanatory. An example CONTRIBUTING.md can be seen here: https://github.com/aptoma/news-portal/blob/develop/CONTRIBUTING.md

As you all know, GitHub renders READMEs beneath the directory listing whenever theres a README in a directory. A link to CONTRIBUTING.md is displayed when people create issues or pull requests.