Bump requests from 2.13.0 to 2.20.0

Bumps [requests](https://github.com/psf/requests) from 2.13.0 to 2.20.0.
- [Release notes](https://github.com/psf/requests/releases)
- [Changelog](https://github.com/psf/requests/blob/master/HISTORY.md)
- [Commits](psf/requests@v2.13.0...v2.20.0)

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

Author: dependabot[bot]

requirements.txt

@@ -12,7 +12,7 @@ plac==0.9.6
 preshed==1.0.0
 pyparsing==2.2.0
 pyzmq==16.0.2
-requests==2.13.0
+requests==2.20.0
 six==1.10.0
 slackclient==1.0.5
 spacy==1.7.3