Add some test case

lib/rucaptcha.rb

@@ -1,4 +1,6 @@
-require 'active_support/core_ext'
+require 'rails'
+require 'action_controller'
+require 'active_support/all'
 require_relative 'rucaptcha/version'
 require_relative 'rucaptcha/configuration'
 require_relative 'rucaptcha/controller_helpers'

lib/rucaptcha/controller_helpers.rb

@@ -13,7 +13,7 @@ module RuCaptcha
 
     def random_rucaptcha_chars
       chars = SecureRandom.hex(RuCaptcha.config.len / 2).downcase
-      chars.gsub!(/[0ol1]/i, (rand(9) + 1).to_s)
+      chars.gsub!(/[0ol1]/i, (rand(8) + 2).to_s)
       chars
     end