HW 16 fix
Merge branch 'master' of https://github.com/thebravoman/software_engineering_2013
Merge branch 'master' of https://github.com/thebravoman/software_engineering_2013
Merge branch 'master' of https://github.com/thebravoman/software_engineering_2013
Merge branch 'master' of https://github.com/thebravoman/software_engineering_2013
HW20 improvement