feat(buttons): hide nested inputs

- Hide nested input elements

Closes #4282

Author: wesleycho

src/buttons/buttons.js

@@ -18,6 +18,8 @@ angular.module('ui.bootstrap.buttons', [])
     link: function(scope, element, attrs, ctrls) {
       var buttonsCtrl = ctrls[0], ngModelCtrl = ctrls[1];
 
+      element.find('input').css({display: 'none'});
+
       //model -> UI
       ngModelCtrl.$render = function() {
         element.toggleClass(buttonsCtrl.activeClass, angular.equals(ngModelCtrl.$modelValue, scope.$eval(attrs.btnRadio)));
@@ -50,6 +52,8 @@ angular.module('ui.bootstrap.buttons', [])
     link: function(scope, element, attrs, ctrls) {
       var buttonsCtrl = ctrls[0], ngModelCtrl = ctrls[1];
 
+      element.find('input').css({display: 'none'});
+
       function getTrueValue() {
         return getCheckboxValue(attrs.btnCheckboxTrue, true);
       }