Merge pull request #15 from Japh/master

Fix minor markdown syntax errors in Chapter 2 props @japh
Merge pull request #17 from Japh/master

Change linking method and fix minor typographical errors
Added books to resources

Added The Cathedral and the Bazaar and Hackers
First draft of Chapter 4

A first draft of chapter 4 which deals with the history of the GPL and
free software foundation, discusses the freedoms of the GPL, copyleft,
and the difference between permissive and copy licenses. Also, why the
GPL is important, and how the GPL came to be WordPress' license.
Merge pull request #19 from smckeown/master

First draft of Chapter 4