[TaiNing] Things to do in Week 8 & Formatting output before passing to GUI

```
1. After Lynnette fixed things in Input Processing, test all functionalities 
and ensure everything works well. If not, find problems and revise code.
2. Implement multiple undo/redo.
3. Refine code. Refactoring. 
4. Try to use assertions, logs, and handle exceptions.
```

Original issue reported on code.google.com by `wangtain...@gmail.com` on 9 Mar 2014 at 8:50
