initial implentation of preview frame, add semi-fade fragment style, data-full-height support
support vertical align of slides with absolute children
Use Math.floor instead of parseInt to avoid problems with very small numbers like 2e-10
started the new per-slide background implementation (#453)
add test directory and simple test document for per-slide backgrounds (#453)
don't transition to first slide background (#453)
support for optional background property overrides (#453)
linear sliding transition option for full page backgrounds (#453)
allow control over background color when using images (#453)
update background test, documented slide backgrounds in readme (#453)
update example deck to use slide backgrounds (#453)
Only call embedded content bits if the slide actually changed.
revamp pdf printing to support per-slide backgrounds (closes #453)
add test deck for embedded media
merge fix for embedded media repeated autoplay
update code style to match after merge
merge notes timer rounding fix
serve notes/multiple index document as html (closes #470)
set 'hidden' attribute on all slides except the present (#457)
semi-correction #470