Use rails instead of rake

This is the recommended approach in the rails guides, plus rake is broken out of the box if you install with windows railsinstaller.

Author: RobinClowers

sites/en/installfest/create_a_rails_app.step

@@ -77,7 +77,7 @@ step "Generate a database model" do
     rails generate scaffold drink name:string temperature:integer
   BASH
   console <<-BASH
-    rake db:migrate
+    rails db:migrate
   BASH
   console <<-BASH
     rails server