minor: merge should be called with parens here

TylerBrock · TylerBrock · commit b10d51cff056 · 2013-03-14T14:09:12.000-04:00
diff --git a/lib/mongo/util/read_preference.rb b/lib/mongo/util/read_preference.rb
@@ -44,7 +44,7 @@ def read_preference
     def read_pool(read_preference_override={})
       return primary_pool if mongos?
 
-      read_pref = read_preference.merge read_preference_override
+      read_pref = read_preference.merge(read_preference_override)
 
       if pinned_pool && pinned_pool[:read_preference] == read_pref
         pool = pinned_pool[:pool]
