update tests for new data model

WIP, don't merge.

The first step here was to fix the webpack stuff for bundling the tests for testem. I updated to latest webpack to do this, since we had regressed versions because of an issue with Joi, which we're no longer using for validation. However, I'm still having a problem with `--devtool eval-source-map` on the tests - webpack hangs halfway through building the modules when it's turned on. I just took it out, but if you have any ideas @nicolashery, would love to hear 'em.