Maintainer update
Use were appropriate and clean up the list a little.
-Chris O'Haver
-Cricket Liu
-John Belamaric
-Manuel Alejandro de Brito Fontes
-Michael Richmond
-Miek Gieben
-Yong Tang
+Chris O'Haver <chris@coredns.io>
+John Belamaric <john@coredns.io>
+Manuel Alejandro de Brito Fontes <aledbf@gmail.com>
+Miek Gieben <miek@coredns.io>
+Yong Tang <yong.tang@coredns.io>
