[authors] [Ping Jean]: reviewed Writer Guide, Chapter 8 (Working with graphics)

[Michele Zarri]

Hello Jean,

I have reviewed chapter 8. Unfortunately I forgot to accept your changes 
and added a few changes of my own.

As far as I am concerned the chapter is ready for version 3.2.

Here's the link:
*http://tinyurl.com/yj7myt9
*
Cheers,

Michele :-D