fault-tolerant implementation of modbus protocol

 This package contains a fault-tolerant, fail-fast implementation of
 Modbus protocol in Go. Supported functions
  - Bit access:
    * Read Discrete Inputs
    * Read Coils
    * Write Single Coil
    * Write Multiple Coils
  - 16-bit access:
    * Read Input Registers
    * Read Holding Registers
    * Write Single Register
    * Write Multiple Registers
    * Read/Write Multiple Registers
    * Mask Write Register
    * Read FIFO Queue