refactored the color class and made it completly immutable (its only
field _argb is now final).
Made 'Screenselection' thread-safe.
- refined the toString-method of 'Color'
- added a test-case for toString
- refactored the test-class for color
cleaned up the main-method.
made Channel partially thread-safe, not sure if it is completly safe.
Merge branch 'master' of https://github.com/greenkeeper/ArduinoLight.git