Embroider support

[steveszc]

This addon won't work in an app built with Embroider because it uses the postprocessTree hook for type=all, which is not supported in Embroider.

Some other addon's with this same issue:
DockYard/ember-service-worker#187
ef4/prember#59

[sir-dunxalot]

Hi @steveszc. Thanks for opening this issue. Unfortunately, I know nothing about Embroider and don't use Ember these days. I'll accept a PR that makes these changes if it doesn't break compatibility with non-Embroider apps. However, it's not likely I will make this change myself.