Moment.js is only used in a single place, for converting ISO8601 date-time strings
from the annotation's 'updated' field to user-friendly
date strings (eg. 'Wednesday 17 Dec, 18:59') for the tooltips
for the last-updated link in the annotation card.

Replacing this with functions from the built-in Date object saves
167KB from the generated bundle size (see
moment/min/moment-with-locales.min.js) and also speeds up the digest
cycle. For 20 annotation cards in the /stream view, generating the
date string used to take 6-7ms with Moment. It takes <2ms with
the built in functions in a current build of Chrome.

This still shows up as the most expensive watch expression, so
we might want to add caching as well.