Polymerised the stick-person.

Moved stick-person html structure to new file stick-person.html and changed index.html to use the polymer element stick-person.

Adjusted the javascript file for a Polymer element.

Changed the background to white and the stick-person to black for generalisability.

R=mikelawther@chromium.org

Review URL: https://codereview.appspot.com/48400043