add SubTasks to Task struct. Change PrintTasks to PrintAllTasks, add recurisve printing function PrintTask().
added TasksRoot, subtasks working
json now prettyprints
removed unnecessary duplication of TaskList calls, moved task_root to global variable
removed debug print line
Merge branch 'subtasks' of http://github.com/takemikazuchi/gotodo
add windows path support
add error handling and fix index
Merge branch 'subtasks'