Declare namespace for storage

[Asmor]

It would be nice to be able to declare a namespace, e.g. store.namespace("foo"). The namespace would then be prepended to all keys, e.g. store.get("key") would be equivalent in this case to store.get("foo-key") if you'd never declared a namespace.

There should also be an option to specify a different namespace on a per-get basis, or even specify that no namespace should be used.