Use yarn, drop node 4,6,7

.travis.yml

@@ -1,8 +1,7 @@
+---
 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
+  - '8'
 
 sudo: false
 dist: trusty
@@ -11,35 +10,43 @@ addons:
   chrome: stable
 
 cache:
+  yarn: true
   directories:
-    - $HOME/.npm
+    - node_modules
 
 env:
   global:
     # See https://git.io/vdao3 for details.
-    - JOBS=1
-  matrix:
+    - JOBS=3
+
+jobs:
+  fail_fast: true
+  allow_failures:
+    - env: EMBER_TRY_SCENARIO=ember-canary
+    - env: EMBER_TRY_SCENARIO=ember-beta
+
+  include:
+    # runs linting and tests with current locked deps
+
+    - stage: 'Tests'
+      name: 'Tests'
+      script:
+        - yarn run lint:js
+        - yarn test
+
     # we recommend new addons test the current and previous LTS
     # as well as latest stable release (bonus points to beta/canary)
-    - EMBER_TRY_SCENARIO=ember-lts-2.12
-    - EMBER_TRY_SCENARIO=ember-lts-2.16
-    - EMBER_TRY_SCENARIO=ember-release
-    - EMBER_TRY_SCENARIO=ember-beta
-    - EMBER_TRY_SCENARIO=ember-canary
-    - EMBER_TRY_SCENARIO=ember-default
-
-matrix:
-  fast_finish: true
-  allow_failures:
+    - stage: 'Additional Tests'
+      env: EMBER_TRY_SCENARIO=ember-lts-2.12
+    - env: EMBER_TRY_SCENARIO=ember-lts-2.16
+    - env: EMBER_TRY_SCENARIO=ember-release
+    - env: EMBER_TRY_SCENARIO=ember-beta
     - env: EMBER_TRY_SCENARIO=ember-canary
+    - env: EMBER_TRY_SCENARIO=ember-default
 
-before_install:
-  - npm config set spin false
-  - npm install -g npm@4
-  - npm --version
+stages:
+  - name: 'Tests'
+  - name: 'Additional Tests'
 
 script:
-  - npm run lint:js
-  # Usually, it's ok to finish the test scenario without reverting
-  #  to the addon's original dependency state, skipping "cleanup".
-  - node_modules/.bin/ember try:one $EMBER_TRY_SCENARIO --skip-cleanup
+  - node_modules/.bin/ember try:one $EMBER_TRY_SCENARIO

config/ember-try.js

@@ -1,4 +1,5 @@
 module.exports = {
+  useYarn: true,
   scenarios: [
     {
       name: 'ember-lts-2.12',