Playbacks of PDF don't work on Safari

[rebeccacremona]

We recently began using wacz-exhibitor for playback in Perma.cc.

A user reported that PDFs were not rendering in Safari; instead, they just saw a blank iframe. We realized it was because we were still setting the sandbox option on RWP, which is known to cause problems in certain circumstances, and which at present is not configurable when using wacz-exhibitor.

This is both a bug report and a feature request :-) We would love to be able to toggle this behavior via a param.