Auto-reload

This is an auto-reload feature. I used it successfully in conjunction with Simpletask Cloudless and BTsync.
But it may have quirks on race conditions.

could solve #92 
@funkyfuture  : I just try the auto-reload with QTodoTxt on MacOs and Windows and I always have an exception here on Windows:

[Errno 13] Permission denied: 'path to my Dropbox file'

Looks like we try to openFileByName before  the file is completely written. It happens only when I close or delete a task on Mac. Creating or modifying a task is correctly replicated.
Adding a (ugly) sleep(1) before loading the file works