Bump requests from 2.3.0 to 2.20.0

Bumps [requests](https://github.com/requests/requests) from 2.3.0 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@v2.3.0...v2.20.0)

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

Author: dependabot[bot]

requirements.txt

@@ -4,7 +4,7 @@ httpretty==0.8.0
 mock==1.0.1
 oauth2client==1.2
 python-dateutil>=2.2
-requests==2.3.0
+requests==2.20.0
 six==1.6.1
 sure==1.2.7
 nose