Update documentation

[paulfalgout]

No description provided.

[lloy0076]

The lack of ... documentation is completely confusing.

It's not even entirely clear if marionette/js/marionette even works (after all, if it's not meant to have backbone as a dependency then what is L69 doing in the package.json?)

Is the idea something like all the things described at https://marionettejs.com/docs/ will just work except they'll not use Backbone at all?

[paulfalgout]

Backbone is in dev dependencies and not the package. But yeah, essentially marionette should be expected to work without backbone, but it will be tested to work with it nearly the same as before. I would expect many if not most people would continue to use marionette with backbone for a while. The docs will likely update in line with a beta release. There's some outstanding issues to resolve first though.