Fix collapse animation

Set class 'in' at the end of the animation to mimick the
behaviour of TWBS js. This removes scrollbars which are
otherwise visible during the animation in certain
configurations (most notably when used inside navbars).

src/collapse/collapse.js

@@ -97,20 +97,19 @@ angular.module('ui.bootstrap.collapse')
 
           if ($animateCss) {
             $animateCss(element, {
-              addClass: 'in',
               easing: 'ease',
               to: { height: element[0].scrollHeight + 'px' }
             }).start().done(expandDone);
           } else {
-            $animate.addClass(element, 'in', {
-              to: { height: element[0].scrollHeight + 'px' }
+            $animate.animate(element, {}, {
+              height: element[0].scrollHeight + 'px'
             }).then(expandDone);
           }
         }
 
         function expandDone() {
           element.removeClass('collapsing')
-            .addClass('collapse')
+            .addClass('collapse in')
             .css({height: 'auto'});
         }
 
@@ -126,19 +125,18 @@ angular.module('ui.bootstrap.collapse')
             .css({height: element[0].scrollHeight + 'px'})
             // initially all panel collapse have the collapse class, this removal
             // prevents the animation from jumping to collapsed state
-            .removeClass('collapse')
+            .removeClass('collapse in')
             .addClass('collapsing')
             .attr('aria-expanded', false)
             .attr('aria-hidden', true);
 
           if ($animateCss) {
             $animateCss(element, {
-              removeClass: 'in',
               to: {height: '0'}
             }).start().done(collapseDone);
           } else {
-            $animate.removeClass(element, 'in', {
-              to: {height: '0'}
+            $animate.animate(element, {}, {
+              height: '0'
             }).then(collapseDone);
           }
         }