REL 0.4

[sappelhoff]

After lots of work during the past few days, I would like to make a 0.4 release that contains lots of bug fixes, API changes, and a more robust and better pybv 🙂

There are still many enhancements that we could do (first and foremost #50), but let's put them into 0.5 and following releases.

I think we can do #54 and #55 before the 0.4 release, and of course #58 needs to be merged, and the int16 issue-fix PR opened and merged.

[sappelhoff]

done: https://github.com/bids-standard/pybv/releases/tag/v0.4.0