Added ActionView::Base.register_template_handler for easy integration of an alternative template language to ERb and Builder. See test/controller/custom_handler_test.rb for a usage example #656 [Jamis Buck]

git-svn-id: http://svn-commit.rubyonrails.org/rails/trunk@694 5ecf4fe2-1ee6-0310-87b1-e25e094e27de