CaseClauseError in assert_has when multiple matches

[randycoulman]

The docs for assert_has say "It'll raise an error if no elements are found, but it will not raise if more than one matching element is found."

But I'm seeing that an assert_has with multiple matching elements is raising a CaseClauseError when it gets back a {:found_many, ...} tuple.

If the docs are correct, it looks like it should be possible to add another clause to Assertions.assert_has. Probably something like:

{:found_many, _found}
  -> assert true

and a test case for this.

refute_has does have a clause for {:found_many, ...}, so no problems there.

I'll work on a PR to address this.