Add a root path (default to /)
This is usefull when the public html isn't in "/" but in "/public" or "/webapp" for example
rename parameter "root" to "app_root"
update README to add app_root
Merge pull request #23 from Youscribe/addRoot

[COOK-2395] Add a root path (default to /)
Revert "Merge pull request #23 from Youscribe/addRoot"

This reverts commit 40079b26d8e5d4a6b6f4c611e15f0d3efc25d4b7, reversing
changes made to 075ed609ce4d4679a6d4fc0008a6bf6080127623.