Added .gitignore, so that `git status` provides focused results
Introduction - Added paragraph to introduction describing the attraction of the tutorial.
Game Overview - Combined grid pictures into pairs and adjusted text to match. Minor grammar corrections.
Chapter 2 minor grammar refactoring
Added \usepackage(flafter) to help images appear after their first reference. Tweaked chapter 2 to match.
Edited chapter 3.  Added action icon via \dothis with raw latex.  Modified common.tex to refer to pharo.png, which is icon-lighthouse-128x128.png taken from http://files.pharo.org/media/logo/.
Merge pull request #1 from bencoman/master

Chapters 1,2,3 and some latex template modifications.