[Neuroimaging] Chris Markiewicz taking over as lead maintainer for nibabel

[Matthew Brett]

Hi,

Just so y'all know, Chris has kindly agreed to take over the role of
lead maintainer for nibabel.

Well, I should say, he had kindly agreed to take on the title, because
the observant among you will know he has effectively been doing that
job for some time.

We nibabelers don't have any real governance docs, but, as my last act
as lead maintainer, I'm going propose the following:

* the lead maintainer has veto power over commits to nibabel
* they should use it only very rarely, when all possible compromises
have been explored.

If anyone disagrees with this little formalization, please do say.

Thanks very much, as ever, to Chris, and good luck with the task, that
you are already doing...

Cheers,

Matthew