Use travis to run build matrix

.travis.yml

@@ -0,0 +1,7 @@
+language: ruby
+rvm:
+  - 1.9.3
+  - 1.8.7
+env:
+  - AR_TEST_VERSION: 3.0.0
+  - AR_TEST_VERSION: 3.2.12

Rakefile

@@ -23,13 +23,5 @@ task :default => [:spec]
 
 desc 'Run all tests'
 task :spec => 'db:create' do
-  ['3.0.0', '3.2.12'].each do |version|
-    ENV['AR_TEST_VERSION'] = version
-    system 'bundle'
-
-    confirmed_version = `bundle exec gem list activerecord | grep 'activerecord ('`
-    puts "\n*** Testing using #{confirmed_version}"
-    system 'bundle exec rspec'
-    exit 1 unless $?.success?
-  end
+  exec 'rspec'
 end