The validation middleware was added multiple times during unittest. The validator was being called multiple times - in which case the date comes in as a date rather than string.  Although this was fixed in the unittests it seems wise to handle this case and just allow the dates to pass through.
Added tests to ensure that dates pass through since they're always valid as date and date-time objects.
Immediate return if there's a date and modified compare to use Object's toString method.
Merge pull request #9 from darrin/master

Allow the date and dateTime validators to tolerate date types...