updated quadratic roots model, added comparison to roots fcn, different...

updated quadratic roots model, added comparison to roots fcn, different methods result in slightly different values, with results are differenced difference is on order of 1e-16

git-svn-id: https://groke.mcmaster.ca/svn/grad/colin/trunk/TableTool@6763 57e6efec-57d4-0310-aeb1-a6c144bb1a8b