Passing current object to conform function

I patched revalidator to pass the current object to the conform method to add the ability to do deeper contextual validations.

Example: My schema has a start date and an end date. 

      startDate: {
        type: 'string',
        format: 'date',
        required: true
      },
      endDate: {
        type: 'string',
        format: 'date',
        dependencies: 'startDate',
        required: true,
        conform: function(v, o) {
          var startDate = new Date(o.startDate);
          var endDate = new Date(o.endDate);

          if(endDate - startDate < 0)
            return false;
          else
            return true;
        },
        messages: {
          conform: 'end date must be after start date'
        }
      }

This allows me to parse the end date and start date and make sure end date is after start date.

Hope this gets pulled in. Great work on the validator!

-Marshall