implemented a simple command pattern
started to add a central class for executing commands which holds the stack + tests
started to implement CommandHandler with according tests
implemented a basic CommandHandler that enables simple Undo/redo functionality
Implementation finished; simple undo redo management
implemented stack size limit
added debug output for undo/redo stack
added label to undo/redo lists
Merge branch 'master' of github.com:juristr/codehacks