Deamonize clockwork

You are able to deamonize a clockwork process with -d using `deamons gem` and take advantage of daemons features like monitor, start, stop , reload etc

`daemons gem` is not required for `clockwork` to work and it is not specified as a dependency.  
It is only used if -d is specified.

`daemons gem` has to be installed thru `gem install` or it has to be specified in the `Gemfile` of the host project

run like:

`clockwork clock.rb -d start`
`clockwork clock.rb -d stop`

    Options
    Usage: clockwork [options] start|stop|restart|run
        -h, --help                       Show this message
            --pid-dir=DIR', 'Specifies an alternate directory in which to store the process ids.
        -i, --identifier=str             An identifier for the process.
        -l, --log                        Redirect both STDOUT and STDERR to a logfile named     [app_name].output in the pid-file directory
            --log-dir                    A specific directory to put the log files into (default location is pid directory)
        -m, --monitor                    Start monitor process.