Merge pull request #98 from liafailboy/working

added four image files for the icon of the buttons. Changed the whole st...
Storing category in a separate textfile
Include list_categories.json in .gitignore
Integrating category storage with ReaderWriter, TaskManager, Controller, and ICommands
Rewrite parser
Fix bug in CommandParser. Substituted FlexiCommandParser with the new CommandParser
Modify TaskManager to use ObservableList
Merge pull request #109 from mikelimantara/working

Use ObservableList
Merge remote-tracking branch 'upstream/observablelist' into working
Show ControlsFX Dialog when error to load files
Added 2 fxml files: RootLayout and TaskOverviewLayout
Merge pull request #110 from mikelimantara/working

Added 2 fxml files: RootLayout and TaskOverviewLayout
Merge with michael
Refactor FXML File names
Debugging ObservableList
Merge pull request #112 from andhieka/working

Working
changed Main
changed fxml on the TaskDetail and added the new methods in IUserInterface