MAINTAINERS: fix jonboulle's email

Fixes #43

Signed-off-by: Jonathan Boulle <jonathanboulle@gmail.com>

MAINTAINERS

@@ -4,6 +4,6 @@ Brendan Burns <bburns@microsoft.com> (@brendandburns)
 Derek McGowan <derek@mcgstyle.net> (@dmcgowan)
 Jason Bouzane <jbouzane@google.com> (@jbouzane)
 John Starks <jostarks@microsoft.com> (@jstarks)
-Jonathan Boulle <jon.boulle@coreos.com> (@jonboulle)
+Jonathan Boulle <jon@nstack.com> (@jonboulle)
 Stephen Day <stephen.day@docker.com> (@stevvooe)
 Vincent Batts <vbatts@redhat.com> (@vbatts)