🐛 imcompatible with lazy ember-engines >= 0.8.0

[Julien Palmas]

Including ember-leaflet inside a lazy ember engine with ember-engines >= 0.8.0 does not work.

See this comment for some background ember-engines/ember-engines#662 (comment)

I've forked ember-leaflet to fix it with and I'll create a PR with my modif.