Add versioning to your documentation

[HealthyPear]

It seems to me that the documentation (read: "the book") always points to the latest development version.

This can lead to issues like #1243 where a user reads something in the documentation, tries to use it and fails because the version installed was the latest release.

I would suggest to,

1. deploy the documentation on a public service that allows for versioning (like e.g. ReadTheDocs
2. add a automatic changelog to your documentation

[CraftSpider]

Another issue opened due to this: #1225