Deprecation warning

I started getting a bunch of deprecation warnings when running `ember serve`:

```
DEPRECATION: Using class based template compilation plugins is deprecated, please update to the functional style: InlineTemplateTransform [deprecation id: template-compiler.registerPlugin]
```

I seem to find `InlineTemplateTransform` only in `ember-cli-inline-template-only-components` when I grep in my node_modules so I guess the problem lies in this plugin.

Reproduce the warnings by running `ember serve` in a project using ember-cli-inline-template-only-components. Inspect the plugin's use of `InlineTemplateTransform` and compare it with the functional template compilation style. Done means the deprecation warning no longer appears when the plugin is used.

Written by the indexing model from the issue text.