fix(tabs): do not change URL when switching tabs

When you switch between tabs angular changes the URL in the location bar
to the base URL of your app (in most cases `/`). This is because angular
intercepts click event on links to load templates and controllers if
needed. But if the href attribute of a `<a>` tag is empty or missing
angular will only change the URL in the location bar to the base URL.
So I added a `target="_self"` attribute to the `<a>` tag to prevent
interception by angular.