After Bootstrap 4 beta release default badge is not working anymore. Bootstrap documentation now uses secondary badges in the first example. I've done the same in Reactstrap docs. I also added few more examples from original bootstrap documentation.

One thing I am not sure about are links in badges. See original docs here. Should we create a whole new component or maybe add new prop to badge component to allow badge links or should they be created the same way as in Bootstrap: by adding a className to link? Also do we even want to include them in Reactstrap documentation?

Thanks for this. I'm going handle the link the same as how Button works, if there is an href and the tag is defaulted, it will become an anchor tag.
Also, as for the default... I am going to just default it to secondary for now. I know you had mentioned in #539 that it should not default to anything and be required, but I am split about it and am erring on the side of not making a breaking change. If anything I would probably keep defaulting it to 'secondary' and add a deprecation message.