Fix FastIO digitalwrite operations within a critical section. Refer to suggestions on: http://arduino.cc/forum/index.php/topic,77120.63.html
closes #13 - rename private variable for LCD bit-mask pin.
closes #15 - comments added to header files and method descriptions.
closes #16 - added critical sections to fastIOs and associated usage on the LiquidCrystal_SR class.
ref #14 - partially closed pending review.