Use example.com instead of parked domain; Brand caps [ci skip]

- Should use example.com as suggested in
  http://tools.ietf.org/html/rfc2606 instead of one that is
  parked by a domain name seller
- Gist is a subdomain of GitHub, or it could
  have been "GitHub Gist"
- GitHub, SoundCloud and SmugMug have particular caps
Merge pull request #148 from randomecho/readme-example.com

Use example.com instead of parked domain; Brand caps [ci skip]