For flexibility to handle TwoWire instances

For flexibility to handle TwoWire instances

I²C bus can be accessed by Wire instance on Arduino Uno but in some other boards, like Arduino Due, it has another I²C bus on different pins. It can be accessed by using Wire1.

This 0.4.0 release gives flexibility to handle those I²C instances. The I²C bus is defined as TwoWire class in Wire.h.
Now I2C_device class handle multiple instances of TwoWire class.

For more details, refer to README.md, Using different I²C bus in Examples section.