Bump urllib3 from 1.23 to 1.24.2

Bumps [urllib3](https://github.com/urllib3/urllib3) from 1.23 to 1.24.2.
- [Release notes](https://github.com/urllib3/urllib3/releases)
- [Changelog](https://github.com/urllib3/urllib3/blob/master/CHANGES.rst)
- [Commits](urllib3/urllib3@1.23...1.24.2)

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

Author: dependabot[bot]

Pipfile.lock

@@ -1,10 +1,11 @@
+-i https://pypi.org/simple/
 boto3==1.9.4
-botocore==1.12.4
-docutils==0.14
-Jinja2==2.10
-jmespath==0.9.3
-MarkupSafe==1.0
-python-dateutil==2.7.3
+botocore==1.12.253
+docutils==0.15.2
+jinja2==2.10
+jmespath==0.9.4
+markupsafe==1.1.1
+python-dateutil==2.8.0 ; python_version >= '2.7'
 s3transfer==0.1.13
-six==1.11.0
-urllib3==1.23
+six==1.12.0
+urllib3==1.24.2