Removed the standard set.

[tvdeyen]

I moved the standard set into its own gem (https://github.com/magiclabs/alchemy-demo_kit) and renamed it to Demo Kit.

Why remove? Because it is a complete stand alone website that should be maintained on its own.

Why the new name? Because the old one was misleading. The new name fits more into the alchemy / chemistry wording we use anyway.