Remove re-implementation of pathForType

[courajs]

The default ember adapter pluralizes the model type: https://github.com/emberjs/data/blob/v2.2.1/packages/ember-data/lib/adapters/build-url-mixin.js#L280 Re-implenting it in the mixin will clobber a user-specified path function from a super class. For example, this setup will erroneously pluralize the type:

// application/adapter.js
export default DS.RESTAdapter.extend({
  pathForType(type) {
    return Ember.String.camelize(type);
  }
});

// thing/adapter.js
import ApplicationAdapter from '../application/adapter.js';
import UrlTemplates from "ember-data-url-templates";
export default ApplicationAdapter.extend(UrlTemplates, {
  urlTemplate: "{+host}{/namespace}/{pathForType}{/id}"
});

[courajs]

Note: I built this PR on top of #9

[amiel]

This makes plenty of sense.

Note that this will break for people directly using the base system adapter nor the RESTAdapter, as I don't think they implement pathForType.

Would you:

1. Rebase on master now that #9 is merged.

2. At least look in to implementing pathForType with super and a deprecation warning. I'm thinking something like:

   // I'm pretty sure a missing super will just return undefined as opposed to error
   let pathForType = this._super(...); 
   if (pathForType) { return pathForType; }
   // A deprecation warning and the original implementation.
   // We will remove all of this in the 1.13 version.

[courajs]

Sure, I'll look into it

[amiel]

Thanks!

[courajs]

So, I noticed pathForType is implemented in the buildURLMixin: https://github.com/emberjs/data/blob/v2.2.1/packages/ember-data/lib/adapters/build-url-mixin.js#L255 Since what this addon does is override buildURL, it doesn't make sense for it to be used in a base adapter where the buildURLMixin isn't used. I think we can skip the deprecation. What do you think?

[courajs]

(I've rebased the branch)

[amiel]

@drspaniel good point. This looks good.