Cecily and Zoomin story views use a document.body that is smaller than
the document.documentElement. We were just clearing the popups on
clicks on the document.body Clicks on the document element (ie, on the
background of the page) were not being trapped, meaning that you
couldn’t dismiss a popup.
Fixing problems caused by c4b76ceb0b:
* We still need to initialise the saver-handler even when syncing to a
server, otherwise offline snapshots can’t be saved
* We need to override the default save template a bit further up the
stack, to avoid the server side serving the offline version of the wiki
at `/`
