Format project with black (#467)

Format with line length 110 to match flake8

make black part of linting check

Update travis spec for updated black requirements

Add diff output for black on failure

update changelog

tests/unit/test_json_serializer.py

@@ -4,16 +4,14 @@ from vcr.request import Request
 
 
 def test_serialize_binary():
-    request = Request(
-        method='GET',
-        uri='http://localhost/',
-        body='',
-        headers={},
-    )
-    cassette = {'requests': [request], 'responses': [{'body': b'\x8c'}]}
+    request = Request(method="GET", uri="http://localhost/", body="", headers={})
+    cassette = {"requests": [request], "responses": [{"body": b"\x8c"}]}
 
     with pytest.raises(Exception) as e:
         serialize(cassette)
-        assert e.message == "Error serializing cassette to JSON. Does this \
+        assert (
+            e.message
+            == "Error serializing cassette to JSON. Does this \
             HTTP interaction contain binary data? If so, use a different \
             serializer (like the yaml serializer) for this request"
+        )