Bump requests from 2.17.3 to 2.20.0

Bumps [requests](https://github.com/psf/requests) from 2.17.3 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@v2.17.3...v2.20.0)

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

requirements.txt

@@ -8,7 +8,7 @@ psycopg2==2.7.1
 PyJWT==1.5.0
 PySocks==1.6.7
 pytz==2017.2
-requests==2.17.3
+requests==2.20.0
 six==1.10.0
 twilio==6.3.0
 urllib3==1.24.2