Show page titles (window.document.title) server- and client-side

An [issue from ages ago](https://github.com/scraperwiki/custard/issues/332) was annoying me, so I fixed it on the train to London.

<del>I didn't have an internet connection, so couldn't look up how to write selenium tests for window titles. Once tests have been written, this should be ready to go.</del>

Tests added. All ready to go @pwaller.