warn if there are unsaved changes fixes issue #170
warn if there are unsaved changes
fixes issue #170

parvmor/codeworld,alphalambda/codeworld,tgdavies/codeworld,parvmor/codeworld,pranjaltale16/codeworld,tgdavies/codeworld,pranjaltale16/codeworld,three/codeworld,stefan-j/codeworld,nomeata/codeworld,alphalambda/codeworld,venkat24/codeworld,alphalambda/codeworld,parvmor/codeworld,pranjaltale16/codeworld,google/codeworld,google/codeworld,venkat24/codeworld,venkat24/codeworld,stefan-j/codeworld,nomeata/codeworld,three/codeworld,nomeata/codeworld,three/codeworld,google/codeworld,stefan-j/codeworld,tgdavies/codeworld