test(accordion): Added test for already fixed issues

Hi,
As we discussed in PR #109, we would need some test to cover the issues.

Here I've added a test to cover the issues when ng-repeat is used inside accordions.

Although the fix affected collapsible directive only and it would be logical to test only that directive, it is not reproducible when it isn't nested with another directive and bindings.

So I decided to add the test directly to accordion groups.

I also checked that the test is failing on codebase before #109, and passes on Chrome, FF  & Opera post fix.

Cheers,
Gleb