Test for equivalence, not for ordering

At the moment, the unit tests for anagrams use `Is.EqualTo` to compare the expect anagrams with the actual anagrams. The problem is that `Is.EqualTo` requires the ordering to be the same, which should not be the case. This PR replaces the `Is.EqualTo` calls with `Is.EquivalentTo` calls that checks for the same elements to be in the collection, but not necessarily in the same order.