Use semver

[ernado]

Please use semantic versioning with tags, like this:

$ git tag v0.0.1
$ git push origin v0.0.1
# ...
 * [new tag]         v0.0.1 -> v0.0.1

So we can pin to specific version instead of using pseudo-versions :)
Note that it is OK to start with v0.0.X versions, because bumping major versions v1 to v2 will require imports update.

Thank you.