Fixed toJs() of the date list property.

Author: kelp404

lib/properties.js

@@ -304,7 +304,7 @@
               results = [];
               for (i = 0, len = value.length; i < len; i++) {
                 x = value[i];
-                results.push(x != null ? x.toJSON() : null);
+                results.push(x != null ? new Date(x) : null);
               }
               return results;
             })();

src/lib/properties.coffee

@@ -181,7 +181,7 @@ class ListProperty extends Property
                 when BooleanProperty
                     value = ((if x? then Boolean(x) else null) for x in value)
                 when DateProperty
-                    value = ((if x? then x.toJSON() else null) for x in value)
+                    value = ((if x? then new Date(x) else null) for x in value)
                 when ListProperty, ObjectProperty, ReferenceProperty
                     value = ((if x? then x else null) for x in value)
                 else