Bump werkzeug from 0.12.2 to 0.15.3

Bumps [werkzeug](https://github.com/pallets/werkzeug) from 0.12.2 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@0.12.2...0.15.3)

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

Author: dependabot[bot]

requirements.txt

@@ -72,6 +72,6 @@ ujson==1.35               # via datapackage-pipelines
 unicodecsv==0.14.1        # via datapackage, tableschema, tabulator
 unidecode==0.4.21         # via awesome-slugify
 urllib3==1.22             # via botocore, elasticsearch, requests
-werkzeug==0.12.2          # via flask
+werkzeug==0.15.3          # via flask
 xlrd==1.1.0               # via tabulator
 xmljson==0.2.0            # via dataflows