add status codes and teapot example

sanic/response.py

@@ -56,6 +56,7 @@ ALL_STATUS_CODES = {
     415: b'Unsupported Media Type',
     416: b'Requested Range Not Satisfiable',
     417: b'Expectation Failed',
+    418: b'I\'m a teapot',
     422: b'Unprocessable Entity',
     423: b'Locked',
     424: b'Failed Dependency',
@@ -63,6 +64,7 @@ ALL_STATUS_CODES = {
     428: b'Precondition Required',
     429: b'Too Many Requests',
     431: b'Request Header Fields Too Large',
+    451: b'Unavailable For Legal Reasons',
     500: b'Internal Server Error',
     501: b'Not Implemented',
     502: b'Bad Gateway',