Bump requests from 2.12.4 to 2.20.0

Bumps [requests](https://github.com/requests/requests) from 2.12.4 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@v2.12.4...v2.20.0)

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

requirements.txt

@@ -3,4 +3,4 @@ coveralls==1.1
 docopt==0.6.2
 py==1.4.32
 pytest==3.0.5
-requests==2.12.4
+requests==2.20.0