Alter behavior of read_multi to match ActiveSupport::Cache::Store

In the base implementation of ActiveSupport::Cache::Store (and all other
implementing stores), an array of strings passed as argument to
read_multi is treated as a single key. In DalliStore, it is treated as
several keys. This alters the spec and implementation of DalliStore's
read_multi to match ActiveSupport::Cache::Store.

lib/active_support/cache/dalli_store.rb

@@ -128,7 +128,6 @@ def delete(name, options=nil)
       # servers for all keys. Keys must be Strings.
       def read_multi(*names)
         names.extract_options!
-        names = names.flatten
         mapping = names.inject({}) { |memo, name| memo[expanded_key(name)] = name; memo }
         instrument(:read_multi, names) do
           results = {}

test/test_active_support.rb

@@ -98,7 +98,9 @@ def cache_key
           assert_equal({}, @dalli.read_multi([x, y]))
           @dalli.write(x, '123')
           @dalli.write(y, 123)
-          assert_equal({ x => '123', y => 123 }, @dalli.read_multi([x, y]))
+          assert_equal({}, @dalli.read_multi([x, y]))
+          @dalli.write([x, y], '123')
+          assert_equal({ [x, y] => '123' }, @dalli.read_multi([x, y]))
         end
       end
     end
@@ -347,7 +349,7 @@ def cache_key
         map.each_pair do |k, v|
           assert_equal true, @dalli.write(k, v)
         end
-        assert_equal map, @dalli.read_multi(map.keys)
+        assert_equal map, @dalli.read_multi(*(map.keys))
       end
     end
   end