added new file of 250 puzzles. will not current work as input. need
to figure out a good way to use it.
Made explicity Cell type which is now aliased to Possibility.

Instead of aliasing Possibility to [Int] Now have explicit Cell data type.
working on sanitizing rows for output. i want to put zeros in output
as well, on a puzzle tha tis too hard, so we can see how far we
really got.
added boardShow function to handle showing of undecided cells.
Merge remote-tracking branch 'origin/typed-cell'
updating my master branch with andrews type code.
Merge branch 'typed-cell'
merging new typed-cell branch that i modified slightly from original.
no need for sanitize row function anymore
removed binary and added it to .gitignore