bug fixed for TimeTask toString method
Changed logic to integrate with UI
moving "help" string into GUI:
so when the command is "help", Logic passes GUI the feedback as usual, and call UI.setHelp()
Added in uncmi and untick commands. More exception catching done to
ensure that commands will not be performed on the wrong type of list.
Merge pull request #61 from cs2103aug2014-w15-3J/Logic

Merge Master with Logic
refactored callAdd() method for Parser