change some syntax

add .gitignore of .DS_Store

fix a small bug

update to ex2.10

update completed 2.1

add folder ch1 and ch2

change the screenshot

add a short introduction of code

fix bugs

add cpp-tips

add a link to cpp-tips

update readme.md add write plan and a link to cpp-tips

Change some syntax of markdown

update some about 2.1

download the source file from the website version for vs2012