Firmware v 2.1, several bug fixes

Thanks to William Phelps - wm (at) usa.net, for several important bug
fixes.    https://github.com/wbphelps/AlphaClock

* Alarm can now be turned off while snoozing
* Day/month adjust from within menu had unpredictable behavior around
certain month/year boundaries.
* Reorganized library into separate .h/.c files
* Renamed default firmware example sketch
* Tested with Arduino 1.0.3.