bump node version to 12 (#212)

Author: locks

.travis.yml

@@ -3,7 +3,7 @@ language: node_js
 node_js:
   # we recommend testing addons with the same minimum supported node version as Ember CLI
   # so that your addon works for all apps
-  - "6"
+  - "12"
 
 sudo: false
 dist: trusty

package.json

@@ -63,7 +63,7 @@
     "typescript": "^3.5.3"
   },
   "engines": {
-    "node": "6.* || 8.* || >= 10.*"
+    "node": ">= 12.*"
   },
   "ember-addon": {
     "configPath": "tests/dummy/config"