Refactoring code

Refactoring index.html to separate out the css and js.  Updated some of
the styling.  Removing green highlighting because it gives the wrong
impression to the user.
Fixed issue

Valid row was not highlighting correctly because grid was not properly
parsing html inputs.  Solved by substituting 0s for empty inputs.
Refactored js added new feature

Added new feature to indicate if row, col, or square contains the same
digit more than once.  Found that is Row, Col, and square methods were
repetitive.  Refactored the row_ id to a class so I didn't have to use
the different methods when trying to find the row of an element.
Merge branch 'master' into gh-pages