Merge branch 'master' into logic/wenhao
Add "delete all"
Added Date
Implemented output for undo
Fix bug with Undo. Issue #61
Merge remote-tracking branch 'origin/ui/victor' into logic/wenhao
Refactored output javadoc
Added parser to parse from string to a date object.
Refer to https://docs.google.com/spreadsheets/d/1A_enIhjFT220EPobggQ3lZ3hyz3evQ9SVA_b3iCm2ko/edit#gid=0
for the list of acceptable date formats

#40
Merge branch 'master' into parser/Victor
Executable
Output for Help
Added output for Exit
Changes in method flow, variable names
Merge branch 'master' into controller/sharon
A lot of changes
Output message for Errors
Merge remote-tracking branch 'origin/ui/victor' into controller/sharon
Added message field to Command Class
Merge branch 'ui/victor' into parser/Victor
Complete HelpHandler