Add explicit example.

Author: mithrandi

tests.py

@@ -536,6 +536,8 @@ def test_replace_missing(self):
         | st.dictionaries(st.text(string.printable), children))
 
     class RoundtripTests(unittest.TestCase):
+        @hypothesis.example({}, {u'%20': None})
+        @hypothesis.example({u'%20': None}, {})
         @hypothesis.given(json_st, json_st)
         def test_roundtrip(self, src, dst):
             patch = jsonpatch.JsonPatch.from_diff(src, dst, False)