add dots to 'author' middle names

[yegor256]

Would be nice to replace this:

@article{pierce94,
  author = {Pierce, Benjamin C and Turner, David N},
}

with this:

@article{pierce94,
  author = {Pierce, Benjamin C. and Turner, David N.},
}

The dots after middle names must be mandatory, I believe. If we can't auto-fix, let's at least complain.