Exercise 03

doing ...
create deltaX and deltaY

keep going...
Make Delta and Mask as a method

to call it ONCE
Merge and solve conflict from TestEx02

OK!
Minor changes

after merge with TestEx02
focalVariety done!

already tested
Add java doc
Implement Ex03 .. DONE

start to test
Test Ex03 Complete!

It can be submited...
Merge pull request #6 from nntung/Tung-dev

Tung dev .. ready for release ver3.0 .. Got it! I will make a release and submit.