Convert to slidify

[jknowles]

The pandoc slidy template is not ideal. Convert slides to slidify.

Do this using a custom slide template that includes:

• Multiple background colors (some slides should have black backgrounds, this is better)
• Add two-column layouts for some concepts and tutorials to maximize available space
• Select a nice highlighter theme for R code so it stands out
• Use the io2012 template, but modify it so it stands out
• Add quiz module to in-bootcamp exercises!