Remove deprecated usages of dependency keys with a leaf @each

[mmun]

See https://deprecations.emberjs.com/v1.x#toc_using-code-each-code-as-a-leaf-node-in-a-dependent-key

[mmun]

@bantic Check out https://travis-ci.org/github/Addepar/ember-charts/builds/664109422?utm_source=github_status&utm_medium=notification

The "Tests" item completes successfully but the second item is failing during yarn and doesn't seem related to my change. Do you think it is acceptable to merge as is?

[mixonic]

@mmun it looks like Travis needs to be told to use Node 10. We're using Node 10 downstream in our consuming app, so it is safe to just bump the version for this library.

[mmun]

@mixonic Cool, let's see...

[mmun]

Success 🚀