Update build tools
Remove `u-linkPseudo`

There are problems with trying to style a 'button' element to look
like a link.

* It cannot be reliably styled to look like a link within any context.
  It can only look like the globally defined, default link.

* It's an unusual UX pattern that doesn't have a clear reason to exist
  in library code.

Preferred approach:

<a href="#" role="button">Text</a>

…with a click-handler to preventDefault. This has wide ranging
screenreader support (changes to button in the accessibility tree),
retains keyboard focus and events, and gets the link style for free.

Close gh-5