Bump data-set

This increments data-set to version 3.0.0

Previously this would fail `h("foo", { 'data-foo': { 'some': 'object' } })` because the native browser dataset would serialize non string values to strings.

data-set v3.0 fixes this and you can correctly store objects on an element and later retrieve them using the `'data-set'` module.

This is a back compat breaking change as people can no longer access their `'data-*'` keys in `.dataset` compliant browsers using `elem.dataset.foo` they have to use `DataSet(elem).foo`

Recommend major version bump if accept.