Update an example that uses the ":contains()" selector

Author: mdmintz

examples/test_contains_selector.py

@@ -4,6 +4,6 @@
 class ContainsSelectorTests(BaseCase):
     def test_contains_selector(self):
         self.open("https://xkcd.com/2207/")
-        self.assert_text("Math Work", "#ctitle")
+        self.assert_element('div.box div:contains("Math Work")')
         self.click('a:contains("Next")')
-        self.assert_text("Drone Fishing", "#ctitle")
+        self.assert_element('div div:contains("Drone Fishing")')