Merge remote-tracking branch 'origin/ui/victor'
Merge remote-tracking branch 'origin/parser/Victor'
Merge remote-tracking branch 'origin/logic/wenhao'
Merge remote-tracking branch 'origin/ui/victor'
Merge remote-tracking branch 'origin/logic/wenhao'
Used UI instead of Input and Output, deleted unused imports
Merge branch 'controller/sharon'
GCal support
Added displayMessage method in UI and Output and their impl files
Merge remote-tracking branch 'origin/ui/sharon' into logic/wenhao
Merge remote-tracking branch 'origin/controller/sharon' into logic/wenhao