Update ember core (#1389)

ghost/admin/.eslintrc.js

@@ -1,6 +1,14 @@
 /* eslint-env node */
 module.exports = {
     root: true,
+    parser: 'babel-eslint',
+    parserOptions: {
+        ecmaVersion: 2018,
+        sourceType: 'module',
+        ecmaFeatures: {
+          legacyDecorators: true
+        }
+    },
     plugins: [
         'ghost'
     ],

ghost/admin/package.json

@@ -36,6 +36,7 @@
     "@tryghost/string": "0.1.5",
     "@tryghost/timezone-data": "0.2.16",
     "autoprefixer": "9.7.2",
+    "babel-eslint": "10.0.3",
     "blueimp-md5": "2.12.0",
     "broccoli-asset-rev": "3.0.0",
     "broccoli-concat": "3.7.5",
@@ -50,7 +51,7 @@
     "ember-ajax": "5.0.0",
     "ember-assign-helper": "0.2.0",
     "ember-auto-import": "1.5.3",
-    "ember-cli": "3.12.0",
+    "ember-cli": "3.14.0",
     "ember-cli-app-version": "3.2.0",
     "ember-cli-babel": "7.12.0",
     "ember-cli-chai": "0.5.0",
@@ -71,7 +72,7 @@
     "ember-cli-uglify": "3.0.0",
     "ember-composable-helpers": "2.4.0",
     "ember-concurrency": "1.1.3",
-    "ember-data": "3.12.4",
+    "ember-data": "3.14.0",
     "ember-drag-drop": "0.4.8",
     "ember-exam": "4.0.5",
     "ember-export-application-global": "2.0.1",
@@ -90,7 +91,7 @@
     "ember-route-action-helper": "2.0.7",
     "ember-simple-auth": "1.9.2",
     "ember-sinon": "4.1.1",
-    "ember-source": "3.12.1",
+    "ember-source": "3.15.0",
     "ember-sticky-element": "0.2.3",
     "ember-svg-jar": "2.2.3",
     "ember-test-selectors": "2.1.0",