Bump werkzeug from 0.10.1 to 0.15.3

Bumps [werkzeug](https://github.com/pallets/werkzeug) from 0.10.1 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@0.10.1...0.15.3)

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

requirements.txt

@@ -2,7 +2,7 @@ Flask>=1.0.2
 Flask-PyMongo==2.3.0
 Jinja2==2.10
 MarkupSafe==1.1.1
-Werkzeug==0.14.1
+Werkzeug==0.15.3
 itsdangerous==1.1.0
 pymongo==3.10.1
 pytz==2018.9