Update sanic from 19.6.3 to 19.9.0 (#567)

Author: pyup-bot

requirements_dev.txt

@@ -5,7 +5,7 @@ bumpversion==0.5.3  # pyup: update minor
 wheel==0.33.0  # pyup: update minor
 cryptography==2.8  # pyup: update minor
 psycopg2-binary==2.8.1  # pyup: update minor
-sanic==19.6.3;python_version>="3.6"  # pyup: update minor
+sanic==19.9.0;python_version>="3.6"  # pyup: update minor
 aiohttp==3.6.0;python_full_version>="3.5.3"  # pyup: update minor
 tornado==6.0  # pyup: update minor
 async_generator==1.10  # pyup: update minor