Added library.

Added the LCD_5110_SPI library to our code.
Test button debounce program.

Added a sketch that uses a Debouncer class to debounce a button and
turn an LED on/off.
Made it easy to use SPI/no SPI.

Added some preprocessor macros and conditionals to make switching
between SPI and shift-out mode easier.
Added debouncing and multiple LEDs.

Blink two LEDs. Add a button push with debouncing to slow down
the blink time.