Test: fixed HTML5 step attribute tests for firefox44

firefox provides element.type==text,
since it does not support the date input type right now.

src/core.js

@@ -1319,7 +1319,7 @@ $.extend( $.validator, {
 
 		// http://jqueryvalidation.org/step-method/
 		step: function( value, element, param ) {
-			var type = element.type,
+			var type = $( element ).attr( "type" ),
 				errorMessage = "Step attribute on input type " + type + " is not supported.",
 				supportedTypes = [ "text", "number", "range" ],
 				re = new RegExp( "\\b" + type + "\\b" ),