Bump requests from 2.18.1 to 2.20.0

Bumps [requests](https://github.com/requests/requests) from 2.18.1 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@v2.18.1...v2.20.0)

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

Author: dependabot[bot]

requirements.txt

@@ -5,6 +5,6 @@ gevent==1.2.2
 greenlet==0.4.12
 grequests==0.3.0
 idna==2.5
-requests==2.18.1
+requests==2.20.0
 terminaltables==3.1.0
 urllib3==1.21.1