Fix: UX: Contribute: Start at top of page

If we navigate via location.path, Safari doesn't
scroll to the top of the page. This is apparent
when navigating from 'hello' to 'contribute,' as
we arrive half-way down the contribute page.

So, use window.location.href, even though it's
not a best practice, because that's what works
(because it causes the browser to refresh the
page).

Change-Id: I2e4c26dcea3b4831ba3951b65eac6745b4ceaf28