re-simplify mailer_spec

spec/lib/roadie/rails/mailer_spec.rb

@@ -4,9 +4,11 @@
 module Roadie
   module Rails
     describe Mailer do
-      base_mailer = Class.new do
+      some_mailer = Class.new do
         cattr_accessor :asset_host
 
+        include Mailer
+
         def initialize(email = nil)
           @email = email
         end
@@ -16,10 +18,6 @@ def mail(options = {})
         end
       end
 
-      some_mailer = Class.new(base_mailer) do
-        include Mailer
-      end
-
       describe "#roadie_options" do
         it "returns Rails' roadie config" do
           allow(::Rails).to receive_message_chain(:application, :config, :roadie).and_return "roadie config"