Initial update to Section 3

[peterhcharlton]

This update contains code for several of the Section 3 chapters. I haven't modified anything in Sections 1 or 2. It's not yet complete, and has the following outstanding to do's:

1. Add in code for some chapters
2. Check for errors in copying code from authors' submissions to GitHub (for instance, I have renamed some files, which may have a knock-on effect when running the code)
3. Run the code for each chapter to make sure it works

[tompollard]

Looks good, thanks Pete, and thanks for highlighting points 2 and 3. We should probably set up a testing framework...I'll add an issue.