Implement resolveEngine and resolveRouteMap

[trentmwillis]

Addressing ember-engines/ember-engines#10.

One change to note: The route-map lookup now expects an isRouteMap property instead of trying to share a symbol between this addon and ember-engines.

cc @dgeb @rwjblue @nathanhammond

[rwjblue]

Using the stamp seems totally fine to me. Can you add a test for that assertion though?

[trentmwillis]

@rwjblue added a test

[nathanhammond]

My only concern is that this sneaks by the feature flag and exists as "dormant" code in apps the moment we release a new version. I'm tempted to delay landing + release until the feature flag is removed.

[nathanhammond]

(Note: code is perfectly reasonable.)

[trentmwillis]

@nathanhammond I'm not sure I agree. Since Ember Beta is currently running with the feature flag enabled by default, I think now would be a good time to start testing this out as well. We can release a beta version of this addon if needed, but I think we should try to have this working by the time Engines are released in 2.8 (so that we can encourage this pattern over the custom resolver provided by the ember-engines addon).

[nathanhammond]

The fact that it'd be a beta of a point release feels ridiculous, but I'd rather match the current Ember beta progress.

@rwjblue is the only one with publish privs, so it'll be his call. 😛

[rwjblue]

emberjs/ember.js#14199

[trentmwillis]

So @rwjblue does that mean this can land 😉

[rwjblue]

Released as v2.1.0

[nathanhammond]

I now relinquish my stick in the mud position. 😄

[ilucin]

@rwjblue You should probably point out somewhere that this release doesn't work with engines < 0.3.0