add exception handling of loading and saving
Merge branch 'master' of github.com:guokr/simbase
fix some bug
merge from remote
add unittest function for judge decreasing probability
Merge branch 'master' of github.com:guokr/simbase
replace from System.out.print to logger
modify:  
1. backup folder to data folder
2. save exception handle
Merge pull request #9 from zjjott/master

merge and add unittest