Bump pyyaml from 3.13 to 5.1

Bumps [pyyaml](https://github.com/yaml/pyyaml) from 3.13 to 5.1.
- [Release notes](https://github.com/yaml/pyyaml/releases)
- [Changelog](https://github.com/yaml/pyyaml/blob/master/CHANGES)
- [Commits](yaml/pyyaml@3.13...5.1)

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

Diff for: 2019-08-06-bob-ross-requirements.txt

@@ -48,7 +48,7 @@ pyparsing==2.4.2
 pyrsistent==0.15.4
 python-dateutil==2.8.0
 pytz==2019.2
-PyYAML==5.1.2
+PyYAML==5.1
 pyzmq==18.0.2
 qtconsole==4.5.2
 scipy==1.3.0

Diff for: dgrtwo-translations/requirements-2019-04-22.txt

@@ -116,7 +116,7 @@ pyrsistent==0.15.7
 pytest==5.3.4
 python-dateutil==2.8.0
 pytz==2019.3
-PyYAML==5.3
+PyYAML==5.1
 pyzmq==18.1.1
 qgrid==1.2.0
 readme-renderer==24.0

Diff for: requirements.txt

@@ -57,7 +57,7 @@ pyparsing==2.3.1
 pytest==4.3.0
 python-dateutil==2.7.5
 pytz==2018.9
-PyYAML==3.13
+PyYAML==5.1
 pyzmq==17.1.2
 qgrid==1.1.1
 qtconsole==4.4.3