Add System V init script

Since beanstalkd 1.6 ``beanstalkd.init`` file was dropped, this script is useful for Red Hat, Debian, etc. and people building RPMs.

This is a shell script in charge of starting and stopping beanstalkd service on System V, compatible with beanstalkd 1.9, verified that works with CentOS 4/5/6. Basically is the same script that was distributed with version 1.5 modified to work with the 1.9 (``-d`` daemonize option has been removed, etc.).