Bump werkzeug from 0.9.4 to 0.15.3

Bumps [werkzeug](https://github.com/pallets/werkzeug) from 0.9.4 to 0.15.3.
- [Release notes](https://github.com/pallets/werkzeug/releases)
- [Changelog](https://github.com/pallets/werkzeug/blob/master/CHANGES.rst)
- [Commits](pallets/werkzeug@0.9.4...0.15.3)

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

Author: dependabot[bot]

requirements.txt

@@ -15,4 +15,4 @@ sendypy==4.0.9
 six==1.9.0
 twitter==1.14.3
 urllib3==1.25.10
-Werkzeug==0.9.4
+Werkzeug==0.15.3