Convert fit-form component to classic layout

[steveszc]

Purpose

Fixes #47

Approach

Converts fit-form component from pods layout to classic layout

Learning

https://cli.emberjs.com/release/advanced-use/project-layouts/

Addons should only use the classic structure for compatibility with either classic or pods-based consuming applications.

[steveszc]

@flexyford Mind giving this a quick look?

[flexyford]

Happy to merge this, but a couple of tests relied on pod structure. Mind fixing those up as well?

[steveszc]

@flexyford Oops I missed the required updates to the /app directory files.
Looks like theres still one test failing now, and its also failing locally.

Unit | Component | form-adapters/ember-changeset/ember-changeset-validations > with a model with validations > validate the form: validating an invalid form fails the validation step

Not really clear to me why that particular assertion would fail due to these changes.

[flexyford]

After looking into this, we found that this test is failing in master and we suspect it is due to an bugfix in poteto/ember-changeset#378.

We are going to merge to file structure update and fix the test prior to a 2.0.0 release.