Remove hardcoding of `isDevelopingAddon`.
Remove hardcoding of `isDevelopingAddon`.

By default `isDevelopingAddon` is `true` when running `ember serve`, `ember test`, or `ember test --server` within the addon itself but `false` when running inside consuming applications.

The way this was previously, always forced `isDevelopingAddon` to be `true`, which makes consuming applications fail JSHint because this addon does.
jelhan/ember-bootstrap,srvance/ember-bootstrap,kaliber5/ember-bootstrap,kaliber5/ember-bootstrap,srvance/ember-bootstrap,jelhan/ember-bootstrap