Added Appraisal to Gemfile and have the default task run all appraisals

Gemfile

@@ -5,3 +5,4 @@ gem "rake"
 gem "ruby-debug"
 gem "aws-s3", :require => "aws/s3"
 gem "sqlite3-ruby", "~>1.3.0"
+gem "appraisal"

Gemfile.lock

 GEM
   remote: http://rubygems.org/
   specs:
+    appraisal (0.1)
+      bundler
+      rake
     aws-s3 (0.6.2)
       builder
       mime-types
@@ -25,6 +28,7 @@ PLATFORMS
   ruby
 
 DEPENDENCIES
+  appraisal
   aws-s3
   mocha
   rake

Rakefile

@@ -10,11 +10,11 @@ $LOAD_PATH << File.join(File.dirname(__FILE__), 'lib')
 require 'paperclip'
 
 desc 'Default: run unit tests.'
-task :default => [:clean, :test]
+task :default => [:clean, :all]
 
 desc 'Test the paperclip plugin under all supported Rails versions.'
 task :all do |t|
-  exec('rake RAILS_VERSION=2.1 && rake RAILS_VERSION=2.3 && rake RAILS_VERSION=3.0')
+  exec('rake appraisal test')
 end
 
 desc 'Test the paperclip plugin.'