Website improvements

• Add the menu:
  • Home: takes you to the front page.
  • Why?: takes you to the overview of the principles
  • Blog: blogroll of posts.
  • Contact: mailto link to you (for now)
• Add sidebar:
  • Way of subscribing to posts (e.g. mailchimp)
  • Link to the RSS feed
• Add the social buttons more and making them always visible over the content (e.g. http://www.jonobacon.com/2017/04/05/canonical-refocus/)
• Add 'Related Posts' section at the bottom of the blog.
• Add blog comments.