update elements and fix some bugs

lib/iron_form_element_behavior.dart

Index: lib/iron_form_element_behavior.dart
diff --git a/lib/iron_form_element_behavior.dart b/lib/iron_form_element_behavior.dart
index 9062f04503f2c2fd61e25483d670f40005807c90..b75314cd222d0eaddac880e82a39be1ddc1bab96 100644
--- a/lib/iron_form_element_behavior.dart
+++ b/lib/iron_form_element_behavior.dart
@@ -22,8 +22,8 @@ abstract class IronFormElementBehavior implements CustomElementProxyMixin {
   /// custom element that uses this behavior should also use
   /// Polymer.IronValidatableBehavior and define a custom validation method.
   /// Otherwise, a `required` element will always be considered valid.
-  /// It's also strongly recomended to provide a visual style for the element
-  /// when it's value is invalid.
+  /// It's also strongly recommended to provide a visual style for the element
+  /// when its value is invalid.
   bool get required => jsElement[r'required'];
   set required(bool value) { jsElement[r'required'] = value; }