Add GHOrganization.listSecurityManagers()

Add support to list Security Managers in a GitHub Organization.

src/main/java/org/kohsuke/github/GHOrganization.java

@@ -378,6 +378,19 @@ private PagedIterable<GHUser> listMembers(final String suffix, final String filt
                 .toIterable(GHUser[].class, null);
     }
 
+    /**
+     * List up all the security managers.
+     *
+     * @return the paged iterable
+     * @throws IOException
+     *             the io exception
+     */
+    public PagedIterable<GHTeam> listSecurityManagers() throws IOException {
+        return root().createRequest()
+                .withUrlPath(String.format("/orgs/%s/security-managers", login))
+                .toIterable(GHTeam[].class, item -> item.wrapUp(this));
+    }
+
     /**
      * Conceals the membership.
      *