Allow multiple matching elements in assert_has (#20)

Fixes #18

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.

This commit fixes that by adding the necessary clause.

lib/phoenix_test/assertions.ex

@@ -15,6 +15,9 @@ defmodule PhoenixTest.Assertions do
       {:found, _found} ->
         assert true
 
+      {:found_many, _found} ->
+        assert true
+
       {:not_found, []} ->
         raise AssertionError,
           message: """

test/phoenix_test/assertions_test.exs

@@ -45,6 +45,12 @@ defmodule PhoenixTest.AssertionsTest do
       |> assert_has("li", "Aragorn")
     end
 
+    test "succeeds if more than one element matches selector and text", %{conn: conn} do
+      conn
+      |> visit("/page/index")
+      |> assert_has(".multiple_links", "Multiple links")
+    end
+
     test "succeeds if text difference is only a matter of truncation", %{conn: conn} do
       conn
       |> visit("/page/index")