Merge branch 'release' into develop
add ass3 files
move code from previous work
add new classes
try using Thread to solve timer problem.
implement timer with low performance.
implments Timer
implement undo/redo
reference bug exists
fix undo/redo bug
undo/redo now support multiple steps
refactor print using dp.
format codes
Merge branch 'develop'
Merge branch 'master' of https://github.com/cwang22/Othello