Downloads git sub dir
##Usage
python get_git_sub_dir.py path/to/sub/dir <RECURSIVE>
is a boolen True or False. Default is True.
##Example
Lets download the docs from twitter bootstrap https://github.com/twbs/bootstrap/tree/master/docs
python get_git_sub_dir.py twbs/bootstrap/docs
If we don't want it to be recursive
python get_git_sub_dir.py twbs/bootstrap/docs False