HTTP Entity Headers (#1127)

* introduced basic entity and hopbyhop header identification

* removed entity headers

* coding style fixes

* remove unneeded header check

* moved from bytes to unicode in headers

* changed list to tuple in empty response statuses

tests/test_response.py

@@ -103,22 +103,24 @@ def test_no_content(json_app):
     request, response = json_app.test_client.get('/no-content')
     assert response.status == 204
     assert response.text == ''
-    assert response.headers['Content-Length'] == '0'
+    assert 'Content-Length' not in response.headers
 
     request, response = json_app.test_client.get('/no-content/unmodified')
     assert response.status == 304
     assert response.text == ''
-    assert response.headers['Content-Length'] == '0'
+    assert 'Content-Length' not in response.headers
+    assert 'Content-Type' not in response.headers
 
     request, response = json_app.test_client.get('/unmodified')
     assert response.status == 304
     assert response.text == ''
-    assert response.headers['Content-Length'] == '0'
+    assert 'Content-Length' not in response.headers
+    assert 'Content-Type' not in response.headers
 
     request, response = json_app.test_client.delete('/')
     assert response.status == 204
     assert response.text == ''
-    assert response.headers['Content-Length'] == '0'
+    assert 'Content-Length' not in response.headers
 
 
 @pytest.fixture