Fixed collapsible issue in accordion

Fix for issue #328 

```js
section.scope.active = false;
if(section.scope === selectSection) {
     //if collapsible is allowed, a tab will toggle
     section.scope.active = collapsible === true ? !section.scope.active : true;
}
```
since active is forced to false before condition check, active of selected item is always true and collapsible has no effect.

Fixing this in this PR