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

@@ -4,7 +4,7 @@ idna==2.5
 pushbullet.py==0.11.0
 python-magic==0.4.13
 PyYAML==3.12
-requests==2.18.1
+requests==2.20.0
 six==1.10.0
 urllib3==1.24.2
 websocket-client==0.44.0