0.0.7: Update PyYAML to 5.1 or better

[rmol]

Require PyYAML >= 5.1,<6.

Fixes #52.

[redshiftzero]

Diff/changelog dependency review done here, all looked good given context in yaml/pyyaml#257. One thing relevant for other updates of this dependency is:

In a future release (after 5.1) yaml.load() will raise an exception if you don’t
explicitly choose the Loader to use.

(though we don't need to worry about this in this repo as we bring in this dependency via vcrpy).

[redshiftzero]

LGTM, when you've done your diff/changelog review, comment as such and merge this in @rmol!

[rmol]

Agreed. I don't see any problems with the updates to 5.1. We do need to make sure that we explicitly use the safe variants of load/Loader wherever possible.

[kushaldas]

We are still missing the different of the source code and review of that based on the actual source tarballs :)

Because it is a dev dependency, not for production.

[kushaldas]

Approving this as this is still a dev dependency. Nothing to do with production usage.