Upgrade to Rails 4.2

* Update boilerplate with `bin/rake rails:upgrade`
* Use test instead of test:all rake task
* Change stylesheet extensions from .css.scss to .scss
* Update docs to use localhost instead of 0.0.0.0 because Rails 4.2
  no longer listens on all addresses by default.

lib/tasks/continuous_integration.rake

@@ -5,7 +5,7 @@ namespace :ci do
 
     puts 'Running "lite" test suite'
 
-    [:environment, 'db:create', 'test:all'].each do |t|
+    [:environment, 'db:create', :test].each do |t|
       Rake::Task[t].invoke
     end
   end