Bump requests from 2.18.4 to 2.20.0

Bumps [requests](https://github.com/requests/requests) from 2.18.4 to 2.20.0. - [Release notes](https://github.com/requests/requests/releases) - [Changelog](https://github.com/psf/requests/blob/master/HISTORY.md) - [Commits](psf/requests@v2.18.4...v2.20.0) Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

requirements.txt

@@ -50,7 +50,7 @@ python-dateutil==2.6.1
 pytz==2017.3
 pyzmq==17.1.0
 qtconsole==4.3.1
-requests==2.18.4
+requests==2.20.0
 retrying==1.3.3
 scikit-learn==0.19.2
 scipy==1.1.0