Alert stack cannot remove elements from deep object array references.

Basically I have something like this:
```html
<div class="alert fade" ng-repeat="alert in obj.alerts" bs-alert="alert"></div>
```

But the code that currently will look for an element called 'obj.alerts' in the scope, rather than 'obj', and then the attribute named 'alerts' on the 'obj'.

This comes with two tests, one of which was passing prior to the fix.

Would you mind doing a release after pulling this in? (I like to use webjars, and it's easier to maintain with real releases.)