Add more maintainers to Nailgun

We have just three maintainers in Nailgun.
More maintainers is required to make review more effective.
And Bulat is excelent candidate to be a maintainer here.
Please look at: http://stackalytics.com/report/contribution/fuel-web/30 and
http://stackalytics.com/report/contribution/fuel-web/90

Change-Id: I294775e44f2dd3348c9b50044c8b1d066d61e9f1

MAINTAINERS

@@ -17,7 +17,7 @@ description:
   Exceptions are when maintainers are actually cores, or when maintainers
   are not available for some reason (e.g. on vacation).
 
-  [1] https://review.openstack.org/#/c/225376/ (to be replaced by html link once merged)
+  [1] http://specs.openstack.org/openstack/fuel-specs/policy/team-structure.html
   [2] https://review.openstack.org/#/admin/groups/664,members
   [3] http://lists.openstack.org/pipermail/openstack-dev/2015-August/072406.html
 
@@ -36,6 +36,10 @@ maintainers:
       email:  akislitsky@mirantis.com
       IRC:    akislitsky
 
+    - name:   Bulat Gaifullin
+      email:  bgaifullin@mirantis.com
+      IRC:    bgaifullin
+
     - name:   Ivan Kliuk
       email:  ikliuk@mirantis.com
       IRC:    ivankliuk