cherry-picked unload message code change
Merge branch 'master' of https://github.com/Stanford-Online/class2go
Merge branch 'master' of https://github.com/Stanford-Online/class2go
alert to warn users if they are using IE that their work won't save
Merge pull request #2093 from Stanford-Online/giulio-ie-alert-1988

Added alert to warn users using IE that quizzes and assignments won't save or submit