Set size of each slab page via pillar (#19)

* make slab size changeable via pillar

* make slab size changeable via pillar for RedHat, too
diff --git a/tests/pillar/memcached_server.sls b/tests/pillar/memcached_server.sls
index 2c6cf3f..5a85c6c 100644
--- a/tests/pillar/memcached_server.sls
+++ b/tests/pillar/memcached_server.sls
@@ -2,6 +2,7 @@
   server:
     enabled: true
     cache_size: 64
+    slabsize: 2m
     bind:
       address: 0.0.0.0
       port: 11211