making arduino work with led display, RTC and phototransistor

***Here I am adding new arduino sketch, this is first (kinda) working version.***

What I did:

* Top line on LED display shows current time (hours and minutes) from real time
  clock. Big 5x10 digits.
* Bottom line shows time until alarm with negative sign, or time past alarm
  with positive sign. Time is represented in hours and minutes. Alarm time
  is hardcoded into the program.
* * Instead of useless blinking colon between hours and minutes, clock has six
    dots for representing seconds in binary.
* First character of bottom line indicates current brightness level of the
  display and ranges from 0 to F.

How I did it:

* Using HT1632 lib to interface with 24x16 led display
* Using RTClib from adafruit to interface DS1307 real time clock
* Reading phototransistor on analog input with internal pull-up enabled
* * 10bit analog input value gets converted to 15 levels of brightness