Bump jinja2 from 2.7.3 to 2.11.3

Bumps [jinja2](https://github.com/pallets/jinja) from 2.7.3 to 2.11.3.
- [Release notes](https://github.com/pallets/jinja/releases)
- [Changelog](https://github.com/pallets/jinja/blob/master/CHANGES.rst)
- [Commits](pallets/jinja@2.7.3...2.11.3)

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

Author: dependabot[bot]

requirements_flask_app.txt

@@ -1,6 +1,6 @@
 Beaker==1.7.0
 Flask==0.10.1
-Jinja2==2.7.3
+Jinja2==2.11.3
 MarkupSafe==0.23
 Werkzeug==0.14.1
 isodate==0.5.1