Add '-rails' to the name of the gem, and the associated files

Author: michael-misshore

critical-path-css.gemspec renamed to critical-path-css-rails.gemspec

@@ -1,4 +1,4 @@
-require 'critical-path-css'
+require 'critical-path-css-rails'
 
 namespace :critical_path_css do
   @base_url = Rails.env.production? ? 'http://example.com' : 'http://localhost:3000'