Closes #1569.

Closes #1163, #1495.

The development workflow can be used with Node 4+, not just Node 6. We
should avoid showing warnings and errors when users are installing this
package via npm/yarn.

Ref. #1729, #1743.
Closes #1725.

The development workflow can be used with Node 4+, not just Node 6. We
should avoid showing warnings and errors when users are installing this
package via npm/yarn.

Ref. #1729, #1743.
Closes #1725.

Expands the details already given by highlighting the defaults for all attributes and clarifying what's required.

more in-depth documentation of slide backgrounds #1542

readme tweaks