Request socket based serial port connection

[mhoffma]

I would like to be able to open a socket stream and not be limited to a hardwired serial connection, this is useful for devices that have Wifi shields or are just plain old wifi devices themselves that have some capability. This firmata protocol works great over a wire with no need to craft a protocol that does the same thing. The ask is to add SocketSerial to the code base.

if port is of the form ipaddr:port then a socket is opened instead of a serial connection. see PL #58