Bump werkzeug from 0.10.4 to 0.15.3

Bumps [werkzeug](https://github.com/pallets/werkzeug) from 0.10.4 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@0.10.4...0.15.3)

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

Author: dependabot[bot]

requirements.txt

@@ -18,7 +18,7 @@ requests==2.7.0
 six==1.9.0
 urllib3==1.12
 webassets==0.11.1
-Werkzeug==0.10.4
+Werkzeug==0.15.3
 WTForms==2.1
 python-dotenv==0.12.0
 psycopg2-binary==2.8.5