Require less of the rails stack so that it's not being imposed on applications that use paper_trail.

paper_trail.gemspec

@@ -15,7 +15,8 @@ Gem::Specification.new do |s|
   s.executables   = `git ls-files -- bin/*`.split("\n").map{ |f| File.basename(f) }
   s.require_paths = ['lib']
 
-  s.add_dependency 'rails', '~> 3'
+  s.add_dependency 'railties', '~> 3.0'
+  s.add_dependency 'activerecord', '~> 3.0'
 
   s.add_development_dependency 'rake'
   s.add_development_dependency 'shoulda',      '2.10.3'

test/dummy/config/application.rb

@@ -4,7 +4,6 @@ require "active_model/railtie"
 require "active_record/railtie"
 require "action_controller/railtie"
 require "action_view/railtie"
-require "action_mailer/railtie"
 
 Bundler.require
 require 'paper_trail'

test/dummy/config/environments/test.rb

@@ -23,7 +23,7 @@ Dummy::Application.configure do
   # Tell Action Mailer not to deliver emails to the real world.
   # The :test delivery method accumulates sent emails in the
   # ActionMailer::Base.deliveries array.
-  config.action_mailer.delivery_method = :test
+  config.action_mailer.delivery_method = :test if config.respond_to?(:action_mailer)
 
   # Use SQL instead of Active Record's schema dumper when creating the test database.
   # This is necessary if your schema can't be completely dumped by the schema dumper,