Crowdfunding promise delivery

[regebro]

These are the things that I promised to do in the crowd funding campaign, https://github.com/regebro/supporting-python-3/issues/new

• Clean up the code (done)
• Document how to generate the HTML for the site (done)
• Move the code to Github (done)
• Rename the book into "Supporting Python 3" (done)
• Update the "About this book" page to reflect the books community status and contributors. (done)
• Create a contributor licensing scheme
• Set up automatic testing
• Set up automatic generation of HTML and PDF's and publish

[regebro]

Create a contributor licensing scheme: Done.