Implement an empty namespace for Clotted Cream

Create an empty namespace, `ClottedCream`, and alias it to the name
`Butter`.

Namespaces, and namespace aliases, can be used to simplify the system of
versioning. `Butter` is the "public" namespace for the library and
always points to the most recent release.

`ClottedCream` is representative of the work done for v0.1.0; that is to
say the initial development release contains no work.