MAINTAINERS: initial commit

Based on election results: https://groups.google.com/a/opencontainers.org/forum/#!topic/tob/B_u26EhnDm8

Which was decided via a vote started in late March: https://groups.google.com/a/opencontainers.org/forum/#!topic/tob/o5DLbYfZxQo

Based on a nomination process started early March: https://groups.google.com/a/opencontainers.org/forum/#!topic/tob/OKQmg0k-9bU

MAINTAINERS

@@ -0,0 +1,7 @@
+Brandon Philips <brandon.philips@coreos.com> (@philips)
+Brendan Burns <bburns@google.com> (@brendandburns)
+Jason Bouzane <jbouzane@google.com> (@jbouzane)
+John Starks <jostarks@microsoft.com> (@jstarks)
+Jonathan Boulle <jon.boulle@coreos.com> (@jonboulle)
+Stephen Day <stephen.day@docker.com> (@stevvooe)
+Vincent Batts <vbatts@redhat.com> (@vbatts)