helm wrapper doesn't include rollback

[nicholasrobertm]

In the docs it's specified that:

With the helm wrapper you can easily run "helm secrets install/upgrade/rollback" with secrets files included as -f option from you helm_vars values dir tree.

However, if you try to run something like helm secrets rollback releasename revision you (rightly) have it fail. Looking at this it looks like this was never implemented? When rolling back it doesn't seem like it does need to decrypt the files and such and re-encrypt them, that said I propose:

To support this option in the wrapper anyway. This will make usage of it more consistent.
To update the documentation with more specific details on how this works.