Add a way to validate min and max value of an integer site setting

lib/validators/email_setting_validator.rb

@@ -1,9 +1,13 @@
 class EmailSettingValidator
-  def self.valid_value?(val)
+  def initialize(opts={})
+    @opts = opts
+  end
+
+  def valid_value?(val)
     !val.present? || !!(EmailValidator.email_regex =~ val)
   end
 
-  def self.error_message(val)
+  def error_message(val)
     I18n.t('site_settings.errors.invalid_email')
   end
 end