Bump gunicorn from 19.3.0 to 19.5.0

Bumps [gunicorn](https://github.com/benoitc/gunicorn) from 19.3.0 to 19.5.0.
- [Release notes](https://github.com/benoitc/gunicorn/releases)
- [Commits](benoitc/gunicorn@19.3...19.5.0)

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

requirements.txt

@@ -52,7 +52,7 @@ fake-factory==0.5.7
 feedparser==5.1.3
 funcsigs==1.0.0
 futures==3.0.3
-gunicorn==19.3.0
+gunicorn==19.5.0
 gyp==0.1
 html5lib==0.999
 httplib2==0.8