Fix dub dependencies' specification

The dependency of "vibe-d" is now specified using a semantic version (">=0.7.19") instead of the deprecated branch specifier ("~master").

The file package.json has also been renamed to dub.json, as recommended by dub now.

Finally, I added a tag v0.0.1 to allow specifying ddb by semantic version, but I think this is not included in the pull request, so the tag should be added in the main repo.