Pass (row, col) to valueFormatter

It's a little crazy that this information isn't already passed through to these callbacks. See the SO question linked to in the issue below. I'd like to include this in a 1.1.1 minor update.

Fixes #520 
Believe it or not, I'm not clear what 'row' and 'col' are without reading the code.

Also, if you're reordering methods, I'd like to see the graph by the first argument for most callbacks (low priority.)