Pull layout and roadie style inlining out into spree's base mailer so it applies to all mailers

app/mailers/enterprise_mailer.rb

@@ -2,9 +2,6 @@ require 'devise/mailers/helpers'
 class EnterpriseMailer < Spree::BaseMailer
   include Devise::Mailers::Helpers
 
-  layout 'mailer'
-  helper Spree::MailerHelper
-
   def welcome(enterprise)
     @enterprise = enterprise
     mail(:to => enterprise.email, :from => from_address,

app/mailers/spree/base_mailer_decorator.rb

@@ -0,0 +1,8 @@
+Spree::BaseMailer.class_eval do
+  # Inline stylesheets
+  include Roadie::Rails::Automatic
+
+  # Define layout
+  layout 'mailer'
+  helper Spree::MailerHelper
+end

app/mailers/spree/order_mailer_decorator.rb

@@ -1,6 +1,4 @@
 Spree::OrderMailer.class_eval do
-  layout 'mailer'
-  helper Spree::MailerHelper
   helper HtmlHelper
   helper CheckoutHelper
   helper SpreeCurrencyHelper

app/mailers/spree/user_mailer_decorator.rb

@@ -1,7 +1,4 @@
 Spree::UserMailer.class_eval do
-  layout 'mailer'
-  helper Spree::MailerHelper
-
   def signup_confirmation(user)
     @user = user
     mail(:to => user.email, :from => from_address,