Use symbol instead of string in RedisCacheable attribute definitions

app/models/concerns/redis_cacheable.rb

@@ -7,7 +7,7 @@ module RedisCacheable
   class_methods do
     def cached_attr_reader(*attributes)
       attributes.each do |attribute|
-        define_method("#{attribute}") do
+        define_method(attribute) do
           cached_attribute(attribute) || read_attribute(attribute)
         end
       end
@@ -15,7 +15,7 @@ module RedisCacheable
 
     def cached_attr_time_reader(*attributes)
       attributes.each do |attribute|
-        define_method("#{attribute}") do
+        define_method(attribute) do
           cached_value = cached_attribute(attribute)
           cached_value ? Time.zone.parse(cached_value) : read_attribute(attribute)
         end