Update pyyaml from 3.12 to 4.1

pyup-bot · pyup-bot · commit 15a18e1f54c6 · 2018-06-27T09:29:47.000+08:00
diff --git a/requirements_dev.txt b/requirements_dev.txt
@@ -5,7 +5,7 @@ bumpversion==0.5.3
 wheel==0.31.1
 watchdog==0.8.3
 cryptography==2.2.2
-PyYAML==3.12
+PyYAML==4.1
 psycopg2-binary==2.7.5
 sanic==0.7.0
 aiohttp==3.3.2
