feat(ionCheckbox): allow ng-disabled attribute

Closes #939.

Author: keithdmoore

Diff for: js/ext/angular/src/directive/ionicCheckbox.js

@@ -27,6 +27,7 @@ angular.module('ionic.ui.checkbox', [])
       ngModel: '=?',
       ngValue: '=?',
       ngChecked: '=?',
+      ngDisabled: '=?',
       ngChange: '&'
     },
     transclude: true,
@@ -41,7 +42,8 @@ angular.module('ionic.ui.checkbox', [])
     compile: function(element, attr) {
       var input = element.find('input');
       if(attr.name) input.attr('name', attr.name);
-      if(attr.ngChecked) input.attr('ng-checked', 'ngChecked');
+      if(attr.ngChecked) input.attr('ng-checked', attr.ngChecked);
+      if(attr.ngDisabled) input.attr('ng-disabled', attr.ngDisabled);
       if(attr.ngTrueValue) input.attr('ng-true-value', attr.ngTrueValue);
       if(attr.ngFalseValue) input.attr('ng-false-value', attr.ngFalseValue);
     }

Diff for: js/ext/angular/test/directive/ionicCheckbox.unit.js

@@ -27,4 +27,14 @@ describe('Ionic Checkbox', function() {
     expect(div.text()).toEqual('INNER TEXT');
   });
 
+  it('should pass down attrs', function() {
+    el = compile('<ion-checkbox ng-checked=1 ng-disabled=2 ng-true-value=3 ng-false-value=4>')(scope);
+    scope.$apply();
+    var input = el.find('input');
+    expect(input.attr('ng-checked')).toBe('1');
+    expect(input.attr('ng-disabled')).toBe('2');
+    expect(input.attr('ng-true-value')).toBe('3');
+    expect(input.attr('ng-false-value')).toBe('4');
+  });
+
 });