improve chapter 6 readability
add chapter06.cpp
merage boshen pull request
Merge pull request #54 from Boshen/chapter06

add chapter 6 cpp code and improve readability
merge sallen450 pull request:Add Chapter 30~31
Merge branch 'master' of https://github.com/julycoding/The-Art-Of-Programming-by-July
Update 06.0.md
Update 06.0.md
Merge pull request #56 from lidashuang/patch-5

Update 06.0.md
Merge pull request #58 from lidashuang/patch-7

Update 06.0.md
Update 06.0.md
Merge pull request #60 from lidashuang/patch-8

Update 06.0.md
Update preface.md
Update preface.md
Merge pull request #8 from julycoding/master

Merge master code to my own repo