Add bump-my-version config

[finsberg]

Now we can bump the version by installing the dev dependencies (i.e [bump-my-verson](https://github.com/callowayproject/bump-my-version. Then you can do

bump-my-version bump patch

(orminor / major instead of patch). This will then create a new commit and tag. So you need to remember to push the tag afterwards (i.e git push --tags)