added ex4.1 ~ 4.2
changed background color suiting for different os
remove exercise on the index
added ex4.3~ex4.19
Update template.html
edit css
edit css more
edit more
edited ex4.19
added ex4.20
changed doc style
merge Mooophy
remove viewdocs and just use Github.
added ex4.25~4.27
Create ex4_28.cpp
Update Format of code.
added ex4.28~4.30
added ex4.31~4.35
Finished Chapter 4 :link:

Remove the viewdocs and move doc to readme file. More simple for writting.
Merge remote-tracking branch 'Mooophy/master'