Add epub metadata & placeholder cover image
Refactor parseBook.py and extend Makefile to enable support for more formats
Update appendix 2
Add book.epub to .gitignore
* Fixes first shader not automatically closing by adding `u_time` (see patriciogonzalezvivo/glslViewer#142).
* Use glslviewer's headless mode for generating images.
* Update to latest Pandoc CLI arguments to fix Pandoc CLI errors.
* Re-encode `12/accretion.jpg` and `13/holdsworth.jpg` to fix Pandoc jpg errors.
* Update appendix 2 README for generating the book as a pdf.