Serial Addressing

[ghost]

This PR adds Serial as the default stream for the library, allowing users of the original library to leave their old firmware alone, while allowing them to use the hardware serial ports on the AtMega32u4, or alternative hardware serial ports on the AtMega2560.

Also added is addressing in the form of setAddress() and addCommandWithAddr() these functions allow developers to have multiple devices on a single serial bus at a time with similar command sets. The example code has been updated to show how one would use these.