improve example of -w in README
improve example of -w in README

dejon97/libsvm,mhdella/libsvm,TKlerx/libsvm,melissa-mccoy/libsvm,caidongyun/libsvm,Maluuba/libsvm,ChinaQuants/libsvm,DaveGeneral/libsvm,caidongyun/libsvm,androidYibo/libsvm,DaveGeneral/libsvm,G-P-S/libsvm,sdgdsffdsfff/libsvm,ChinaQuants/libsvm,androidYibo/libsvm,Guokr1991/libsvm,androidYibo/libsvm,TKlerx/libsvm,caidongyun/libsvm,asifmadnan/libsvm,G-P-S/libsvm,melissa-mccoy/libsvm,androidYibo/libsvm,Guokr1991/libsvm,phoenixstar7/libsvm,Guokr1991/libsvm,Guokr1991/libsvm,asifmadnan/libsvm,mhdella/libsvm,dejon97/libsvm,Guokr1991/libsvm,dejon97/libsvm,caidongyun/libsvm,cjlin1/libsvm,cjlin1/libsvm,TKlerx/libsvm,melissa-mccoy/libsvm,TKlerx/libsvm,cjlin1/libsvm,mhdella/libsvm,sdgdsffdsfff/libsvm,phoenixstar7/libsvm,cypro666/libsvm,phoenixstar7/libsvm,Adoni/libsvm,dejon97/libsvm,cypro666/libsvm,caidongyun/libsvm,mhdella/libsvm,cypro666/libsvm,melissa-mccoy/libsvm,G-P-S/libsvm,TKlerx/libsvm,mvtuong/Yelp-Challenge,Adoni/libsvm,asifmadnan/libsvm,DaveGeneral/libsvm,cypro666/libsvm,cjlin1/libsvm,Maluuba/libsvm,toothacher17/libsvm,ChinaQuants/libsvm,Guokr1991/libsvm,toothacher17/libsvm,TKlerx/libsvm,mhdella/libsvm,sdgdsffdsfff/libsvm,asifmadnan/libsvm,androidYibo/libsvm,Maluuba/libsvm,mvtuong/Yelp-Challenge,caidongyun/libsvm,sdgdsffdsfff/libsvm,cypro666/libsvm,androidYibo/libsvm,G-P-S/libsvm,phoenixstar7/libsvm,toothacher17/libsvm,mhdella/libsvm,asifmadnan/libsvm,ChinaQuants/libsvm,G-P-S/libsvm,phoenixstar7/libsvm,DaveGeneral/libsvm,asifmadnan/libsvm,ChinaQuants/libsvm,cjlin1/libsvm,dejon97/libsvm,melissa-mccoy/libsvm,Maluuba/libsvm,ChinaQuants/libsvm,phoenixstar7/libsvm,toothacher17/libsvm,DaveGeneral/libsvm,Maluuba/libsvm,melissa-mccoy/libsvm,cjlin1/libsvm,Maluuba/libsvm,toothacher17/libsvm,mvtuong/Yelp-Challenge,sdgdsffdsfff/libsvm,Adoni/libsvm,dejon97/libsvm,G-P-S/libsvm,cypro666/libsvm,Adoni/libsvm,toothacher17/libsvm,DaveGeneral/libsvm,sdgdsffdsfff/libsvm,mvtuong/Yelp-Challenge