Allow using the DemoKit with the latest version

Assuming the latest version doesn't break the demo data, you should be able to install the DemoKit with the latest alchemy_cms since it says the following upon installation:
> == First time Alchemy user?
> 
> Then we recommend to install the Alchemy demo kit.

> Just add `gem "alchemy-demo_kit"` to your apps Gemfile and run `bundle install`.