Implemented path::is_dir and other misc path stuff

Path::is_dir simply returns 1 or 0 as to whether the complete path instance
ends in a directory.

Wrote placeholder for path::append. Just returns 1 for now.

Moved delim variable from constructor into a public class level so other
methods could share (be nice!)
Converted constructor to use path::is_dir()

Was calling sys.stat to check if the given path ended at a dir or a file. As of
the previous commit, that functionality has been moved into the path class.
This should help with organization
Just added a comment to path::create()
Updated the todo list
Implemented better recursive note listing

Was just displaying the note name without any indication that it was a note
contained within a subdirectory of the base notes directory. Now it displays
dir/note_name.

Incidentally, this breaks the auto-open functionality for all note types, sub
or not. A fix is soon to come.
Fixed edit bug created by last commit

Was opening the editor on the base directory when trying to edit any note,
rather than opening the note for edit.

The issue was caused by using the wrong variable to set the class variable
_path, which is used when editing notes.
Updated TODO list