Stats file to prevent overwrite

Will check destination file before attempting to write.
--force flag added to force overwriting of files
Added todo.otl file to .gitignore.
README updated to include force flag and new offset syntax
Errors handled a bit better :-S
Improved arg handling

Alias for existing flags
- -S, --show
- -s, --season
- -o, --offset
- -f, --force

New help option (-h, --help)
Gets shouty if no args passed.
Gets shouty if args passed aren't existing files