Update 2.md

Fixing typo.
Update the "Why choose" list

This is a start. 

Need more things. I would like to see a list for the vast API included in the last bullet point. I don't know the complete list. Maybe: sprite (atlas, sheet), actions, animations (including skeletal), particles, transitions, timers, events (touch, keyboard, accelerometer, mouse), sound, file IO, persistence
Added a list of examples for the vast API available

This list needs to be updated.
Merge pull request #16 from kr15to/patch-1

Thank You
Merge pull request #17 from kidproquo/master

Make the why choose list more comprehensive
Add content for chapter 11 about `call custom c++ from lua` and `bind a c++ class to lua automatically`
Merge pull request #14 from RaoZiJian/master

Add Coordinate Systems in Chapter 6
Merge branch 'master' of https://github.com/chukong/programmers-guide
Merge pull request #18 from samuele3hu/master

Add content for chapter 11 about `call custom c++ from lua` and `bind a c++ class to lua automatically`
conventions section
typos
conventions section
Update 2.md

- Minor editing for readability.
- changing sample code to follow conventions used in this book.
modify indentation
modify format
fix indentation problems
adjust text format
Update outline.md

minor fixing, to improve readability.
add more describe to the new ui label
modify some parts of BMFont