#23 Fix issue #22 : Highlight fields with values not passing validation

Thanks for that contrib, it's always better when the inputs yell by themselves ;-)

• Wouldn't that suit better ? https://docs.djangoproject.com/en/1.9/ref/forms/api/#styling-required-or-erroneous-form-rows

• Please use same color as error message boxes : #a9444

As this PR is nearly 1 year old and it does not provide any significative change to existing code base ; we can close without merging it