script: update_hook.sh now update better the scripts
script: update_hook.sh now update better the scripts

Summary:
 * Directory management
 * Symlink follow
 * Check if new version needed

The script didn't manage that well when hooks were in directory or
subdirectory, so this should work better. It also now check if the file
changed or not, to refresh it if need be, and finally follow better the
symlink.

cycloidio/cycloid-hooks,cycloidio/cycloid-hooks