#160 implement function 0x02 in modbus master
#160 add test for function 0x02 in modbus master
#160 implement function 0x04 in modbus master
#160 add test for function 0x04 in modbus master
#160 funcion name 0x03 similar to the rest of the functions
#160 implement function 0x05 in modbus master
#160 add test for function 0x05 in modbus master