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

@@ -9,6 +9,6 @@ boto==2.31.0
 #ply==3.4
 #pycrypto==2.6
 #wsgiref==0.1.2
-gunicorn==19.3.0
+gunicorn==19.5.0
 #pyOpenSSL==0.15.1