Day 10: fix ui bugs

Finally fixing the UI bugs.  (there is still a small pity, cannot set
the feedbackText color.
But, well, the major problem fixed. Rewrite the paintComponent methods
of the feedbackText panel is fine.

And, now i could refer
http://www.oracle.com/technetwork/java/painting-140037.html
and
http://docs.oracle.com/javase/tutorial/uiswing/

for java swing tutorial