Couple of small Newsletter fixes

1) The route /email/campaign was broken in
ceeb7bf5317d7133bf8726b779584fb0a26daafe.  the method
getNextCampaignSchedule() was removed.
e.g. http://meta.telesc.pe/email/campaign
2) The wrong comment count helper was used in the newsletter template
resulting in it being undefined and so you wouldn’t see a count. I’m
guessing this was broken when the post schema was changed as it comes
from a post’s document.
Merge pull request #655 from shambles/newsletter-comment-fix

Couple of small Newsletter fixes