Introduction/Design Patterns Revisited - Markdown

This commit includes Markdown edits to all Game Programming Patterns
chapters through State.

Committing this now in case I mess something up when trying to run the
script or merge changes!
Merge branch 'master' of https://github.com/munificent/game-programming-patterns
Merge branch 'laurenbee-master'
Fix apostrophes on year abbreviations.
Regenerate HTML.