Add Makefile for ePub/PDF generation

This PR essentially puts everything you have in the [other formats](http://kris.shaffermusic.com/2013/09/publishing-with-github-pages/) section of this blog posts into a single easy-to-run command. You can now generate a PDF with `make pdf` and an ePub with `make epub`. It does all of the Markdown copying/header reformatting automatically...all you have to do is change some variable in the Makefile before you run it. 

Requires Pandoc, but so does the blog post I was working from. (It uses pandoc for PDF generation as well, instead of multimarkdown/latexmk.) It also requires `make`, but if they have pandoc the chances are pretty good they have make as well...it's preinstalled on every machine I've ever used. 

Let me know what you think!