Move Hext's website to its own git repository

[thomastrapp]

Move the source of Hext's website to its own git repository to allow for rapid and painless changes to documentation and installation instructions.

Things to consider:

• Improve automation (e.g. git clone hext-site && ./hext-site/build.sh)
• Using Github Pages might be a good idea (CDN, uptime, SSL)
• SSL certificate, e.g. from letsencrypt.org
• Serve hextserver ("Try Hext in your browser") through its own domain + SSL certificate
• Update dependencies (Jekyll, ACE, Semantic UI, Proxygen)
• Cleanup

Edit: See https://github.com/thomastrapp/hext-website