'Multiple definition of' error when including in multiple files.

[Lodevd]

When including this library in multiple files you get the the following error(s):

(.text+0x0): multiple definition of `Modbus::Modbus(unsigned char, Stream&, unsigned char)'

This is easily solved with the following modifications:

1. Placing a "ifndef" around the header code.
   #ifndef MODBUS_RTU_H
   #define MODBUS_RTU_H
   ....
   #endif

2. creating a ModbusRtu.cpp file to split definition from declaration.
   All code down from the next line must be moved to the .cpp file.
   /* PUBLIC FUNCTIONS________________________________________________ */

3. and obviously include the header file at the top of the .cpp file. :)
   #include <ModbusRtu.h>