Overrode getters for managers in StubManagerHolder to use the stub
managers.
Fixed bug in DateParser (not terminating early when date/time is found).
Shifted old add command test cases from CommandParserTest to
AddCommandTest.
Updated StubManagerHolder to support testing of AddCommand.
Merge branch 'master' of https://github.com:443/cs2103aug2014-w11-1j/main.git