Create gh-pages site to view examples from book

[jonathandinu]

Hi Ritchie!

I created a gh-pages branch of all the examples in the book so that you can view/interact with them directly on the web. To merge this you will need to create a gh-pages branch on your base fork but once you do I can PR my gh-pages branch to that one. You can see an example on my fork here: http://jay-oh-en.github.io/d3-book/examples_and_figures.html

Either way (if you want it or not), I will take down the gh-pages site from my own fork.