validateUserInput modified
Merge remote-tracking branch 'origin/xjy-parser'

Conflicts:
	test/application/TestParser.java
temporary tooltip implemented
implemented grouping for the left panel
merge with master
settled the initial design for date
merge with tys-v0.4
fix #177 display id instead of internal id
close #174 completed at sort for events
close #180, sort end date after priority
priority null pointer fixed
fix showing of next date in events
parser.getCommandInfo() throws an exception when invalid user input is entered
Merge remote-tracking branch 'origin/xjy-parser' into sun-v0.4
Merge remote-tracking branch 'origin/xjy-parser' into sun-v0.4
catch invalid command exception
Merge branch 'sun-v0.4' of github.com:cs2103aug2014-w14-2j/main into sun-v0.4

Conflicts:
	test/application/TestParser.java
Extracted backup and undo to separate component
Fixed bug with cloning tasks
Merge branch 'hyungjon-datastorage' into sun-v0.4