Update README.md, link for rubyonrails.org

remove extra 'http://'
allow compass-rails without asset pipeline on Rails 3.2
remove rails 2.3 support
removed rails 2.3 test
add ruby 2.0 to travis
added travis ci build status
Merge pull request #56 from renchaoevee/patch-1

Update README.md, link for rubyonrails.org
merged in PR #64
fix generated_image_url when generated_images_dir is set
Merge branch 'fix_generated_image_url' of github.com:s12chung/compass-rails into rails4
updated compass dependency to latest alpha for testing
Merge