Fix a couple deprecations and update Ember CLI Babel

The `errors.unknownProperty` accessor would initialise the property
on every attempt to access. If this happens more than once during a
render cycle, newer Ember will complain since it is highly inefficient.
See emberjs/ember.js#13948 for more details.

Also removes the use of the `getOwner` polyfill, which was added
natively to `Ember.getOwner` in Ember 2.3.

Lastly updates the dependency on `ember-cli-babel` to be in line with
newer Ember CLI requirements.

addon/errors.js

@@ -4,12 +4,13 @@ const {
   A: emberArray,
   Object: EmberObject,
   get,
-  set
+  set,
+  run
 } = Ember;
 
 export default EmberObject.extend({
   unknownProperty(property) {
-    set(this, property, emberArray());
-    return get(this, property);
+    run.once(() => set(this, property, emberArray()));
+    return emberArray();
   }
 });

addon/mixin.js

@@ -1,7 +1,6 @@
 import Ember from 'ember';
 import Errors from 'ember-validations/errors';
 import Base from 'ember-validations/validators/base';
-import getOwner from 'ember-getowner-polyfill';
 
 const {
   A: emberArray,
@@ -19,7 +18,7 @@ const {
 } = Ember;
 
 const setValidityMixin = Mixin.create({
-  isValid: computed('validators.@each.isValid', function() {
+  isValid: computed('validators.@each.isValid', function () {
     let compactValidators = get(this, 'validators').compact();
     let filteredValidators = compactValidators.filter((validator) => !get(validator, 'isValid'));
 
@@ -29,7 +28,7 @@ const setValidityMixin = Mixin.create({
   isInvalid: not('isValid')
 });
 
-const pushValidatableObject = function(model, property) {
+const pushValidatableObject = function (model, property) {
   let content = get(model, property);
 
   model.removeObserver(property, pushValidatableObject);
@@ -41,8 +40,8 @@ const pushValidatableObject = function(model, property) {
   }
 };
 
-const lookupValidator = function(validatorName) {
-  let owner = getOwner(this);
+const lookupValidator = function (validatorName) {
+  let owner = Ember.getOwner(this);
   let service = owner.lookup('service:validations');
   let validators = [];
   let cache;
@@ -118,7 +117,7 @@ export default Mixin.create(setValidityMixin, {
     this.buildValidators();
 
     this.validators.forEach((validator) => {
-      validator.addObserver('errors.[]', this, function(sender) {
+      validator.addObserver('errors.[]', this, function (sender) {
         let errors = emberArray();
 
         this.validators.forEach((validator) => {

package.json

@@ -44,8 +44,7 @@
     "ember-addon"
   ],
   "dependencies": {
-    "ember-cli-babel": "^5.1.6",
-    "ember-getowner-polyfill": "^1.0.0"
+    "ember-cli-babel": "^6.6.0"
   },
   "ember-addon": {
     "configPath": "tests/dummy/config"