Made broadcast option available via PHP

[mrwhale]

Added in broadcast option. just needed to set socket_option in the send command function This enabled PHP to send to broadcast address, but also still works when specifying specific address

Also added function so when you don't specify an IP in milight constructor it will automatically create it using the broadcast address for the LAN $milight = new Milight();

Known issues- Unable determine subnet mask of server with PHP, so this function will assume everyone is on a /24 subnet relates to issue #3