Solve security vulnerabilities

[vpetersson]

Snyk reported a number of vulnerabilities. We should update and patch them.

[umeboshi2]

Ansible has been using only yaml.safe_load() since v1.1. The suggested fix in PyYaml is to rename .load() to dangerous_load() and defaulting to safe_load behavior on the .load() function. This should be fixed in pyyaml 4.2. Until then, since only ansible seems to be using it, and it uses it safely, this shouldn't be a problem for screenly. (yaml/pyyaml#207)

https://github.com/ansible/ansible/blob/stable-2.5/changelogs/CHANGELOG-legacy.rst#11-mean-street----422013

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.