Implement the initial addon

[GavinJoyce]

This addon should migrate component templates to be co-located as per emberjs/rfcs#481

We can likely leverage some of https://github.com/rwjblue/ember-module-migrator as it does similar things.

Initial todos:

• Manually create some apps with non-colocated components (nested, template only etc.)
  • Classic App
  • Pods App (see this comment)
• Create manual migration PRs (to learn what the codemod needs to do)
  • Classic App
  • Pods App (see this comment)
• Decide on architecture of codemod
  • Do we need to modify any javascript? If not, the codemod will likely be much simpler
• Implement MVP for Classic app (allowing a path to support "folder + index" style too) : Implement initial codemod #2

[GavinJoyce]

Thinking about this a little more, I think this addon should focus on migrating a classic app only. We could create a separate codemod, at some point, to migrate from pods to a classic structure. That would mean that any future classic -> future codemods wouldn't have to concern themselves with the complexity of supporting pods