Parser & Embed: no need to parse at read-time.

This gets rid of the `ready` state added to new DZIs.
Embed: re-add query string support; improve!

Now it should be mostly compatible with old Zoom.it embeds.

The only significant change is a lack of predictable IDs by default,
but to make up for it, I made the ID specifiable too.
View page: use embed for now.
Merge pull request #46 from zoomhub/embed-improvements

Embed improvements