fix bug(using invalid mruby code)

Not use inline mruby code in handler of file
remove duplicated prefix

Nginx::NGX_XXX is duplicated and verbose.
Nginx::XXX is better.
Add regexp engine
Add Nginx::remove_global_variable and update mruby
Update README.md
Update README.md
Update README.md
Update README.md
Update README.md
Update README.md
Update README.md
Update README.md
Update README.md
Update README.md
Update README.md
Update README.md
Update README.md
Update README.md
Update README.md
Update README.md