Make TaskManager a singleton class
Finish converting list of tasks to JSONObject
Merge branch 'master' into storage

Conflicts:
	src/list/AddCommandTest.java
	src/list/Category.java
	src/list/Date.java
	src/list/DeleteCommandTest.java
	src/list/DisplayCommandTest.java
	src/list/EditCommandTest.java
	src/list/TaskManager.java
Finish converter for TASKS
Merge pull request #34 from mikelimantara/storage

Converter Class able to parse list of task to Json and vice versa
Merge pull request #35 from liafailboy/working

added to make the string TODAY or TOMORROW if the date is the day. Minor...
Reduced the scope of today and tomorrow variables
Merge pull request #37 from liafailboy/working

Added the task number on the tasks
nothing to commit
Merge branch 'master' into working
Basic template for FlexiCommandParser
Merge pull request #39 from andhieka/working

Basic template for FlexiCommandParser
Refactored AddCommand to use simpler constructor. Added CommandExecutionException. Separated Tests into a separate folder.
Refactor time to date
Refactored EditCommand to use simpler constructor
Added setTaskNumber in EditCommand
Refactored EditCommandTest to use simpler constructor
Added CommandExecutionException to DeleteCommand.execute()
Refactored DisplayCommand
Applied singleton pattern to UserInterface. Edited CloseCommand