modified:   todo.sh
Updated usage information and added ability to mark multiple files as being
completed.
	modified:   regular.txt
	modified:   todo.sh
Added functionality to add regular tasks.

Changed db array looping format to for(( )) to stop bugs seemingly caused by
the IFS. Also, by starting at index '1', it's simple to skip over the header
line of the db file.
Reorganised and reformatted code.