This library is based heavily on the arduino core library of the same name

It should remain 100% code compatible with that library, from the API perspective.

Support is added to use shift registers to drive the LCD, as well as a custom callback function
to handle pushing bits to the LCD in any imaginable way. The library handles all everything about what
to send and when, and the callback only sets the actual pins and the pulsing of the enable pin.

To accomplish this, the main difference is that the send function no longer always sends a full command or
byte of data, but sends a "chunk" of data, according to 4 bit or 8 bit mode. This allows even initialization
sequences to be sent through the "send" function and therefore the callback as well, if used.