IG versioning, milestones and continuous delivery

[Censacrof]

Since this Implementation Guide is something to which a few different things will have to conform to, i suggest that from now on we use some kind of versioning (i suggest Semantic Versioning). This way it's possible to say to which version of this IG something conforms to.

I also suggest the use of Milestones so that we can plan which issue to solve before the next release and prioritize them.

I think it would be beneficial for the project if instead of making big releases once in a while, we were to make small releases very often, so that we can get feedback as fast as possible. Since CI is already setup in this repo it should be very easy to do continuous delivery / deployment.