Ensures the pid directory exists

Ensures the PID_DIRECTORY exists in order to survive hard reboots. When the machine gets restarted, the script cannot successfully start because the /var/run/$APP_NAME directory does not exist.

This commit addresses this issue creating the directory if it is not existent.
This should probably be surrounded in a ```if [[ ! -d $PID_DIRECTORY ]] ; then...fi```. Also, I am curious why the -p flag is necessary. Ive never seen a linux distro without a /var/run.