feat(accordion): add bound panel-class support

- Add `@` binding support for `panel-class`

Closes #5368
Closes #5596

Author: Daniel Blanco

src/accordion/accordion.js

@@ -64,6 +64,7 @@ angular.module('ui.bootstrap.accordion', ['ui.bootstrap.collapse'])
     },
     scope: {
       heading: '@',               // Interpolate the heading attribute onto this scope
+      panelClass: '@?',           // Ditto with panelClass
       isOpen: '=?',
       isDisabled: '=?'
     },

src/accordion/docs/readme.md

@@ -33,6 +33,7 @@ The body of each accordion group is transcluded into the body of the collapsible
   Whether accordion group is open or closed.
 
 * `panel-class`
+  <i class="glyphicon glyphicon-eye-open"></i>
   _(Default: `panel-default`)_ -
   Add ability to use Bootstrap's contextual panel classes (panel-primary, panel-success, panel-info, etc...) or your own.  This must be a string.
 

src/accordion/test/accordion.spec.js

@@ -610,8 +610,8 @@ describe('uib-accordion', function() {
       });
     });
 
-    describe('uib-accordion group panel class - #3968', function() {
-      it('should use the default value when panel class is falsy', function() {
+    describe('uib-accordion group panel class', function() {
+      it('should use the default value when panel class is falsy - #3968', function() {
         element = $compile('<uib-accordion><uib-accordion-group heading="Heading">Content</uib-accordion-group></uib-accordion>')(scope);
         scope.$digest();
         groups = element.find('.panel');
@@ -623,13 +623,26 @@ describe('uib-accordion', function() {
         expect(groups.eq(0)).toHaveClass('panel-default');
       });
 
-      it('should use the specified value when not falsy', function() {
+      it('should use the specified value when not falsy - #3968', function() {
         element = $compile('<uib-accordion><uib-accordion-group heading="Heading" panel-class="custom-class">Content</uib-accordion-group></uib-accordion>')(scope);
         scope.$digest();
         groups = element.find('.panel');
         expect(groups.eq(0)).toHaveClass('custom-class');
         expect(groups.eq(0)).not.toHaveClass('panel-default');
       });
+      
+      it('should change class if panel-class is changed', function() {
+        element = $compile('<uib-accordion><uib-accordion-group heading="Heading" panel-class="{{panelClass}}">Content</uib-accordion-group></uib-accordion>')(scope);
+        scope.panelClass = 'custom-class';
+        scope.$digest();
+        groups = element.find('.panel');
+        expect(groups.eq(0)).toHaveClass('custom-class');
+        
+        scope.panelClass = 'different-class';
+        scope.$digest();
+        expect(groups.eq(0)).toHaveClass('different-class');
+        expect(groups.eq(0)).not.toHaveClass('custom-class');
+      });
     });
   });
 });