Added ability to add callback inside the switch definition

[perara]

Usage:

    switches = [
      ['-h', '--help', 'Show Help']
      ['-i', '--interval [INTERVAL]', 'Ping Interval', (key, val)->
        console.log "Interval is" + val
      ]
      ['-s', '--packetsize NUMBER', 'Packetsize', (key, val)->
        console.log "Packet Size is " + val
      ]
    ]

This removes some duplicate code.