Use yarn instead of npm

.travis.yml

@@ -12,8 +12,7 @@ addons:
   chrome: stable
 
 cache:
-  directories:
-    - $HOME/.npm
+  yarn: true
 
 env:
   # we recommend new addons test the current and previous LTS
@@ -35,17 +34,19 @@ matrix:
     - env: EMBER_TRY_SCENARIO=ember-canary
 
 before_install:
-  - npm config set spin false
-  - npm install -g npm@4
-  - npm --version
+  - curl -o- -L https://yarnpkg.com/install.sh | bash
+  - export PATH=$HOME/.yarn/bin:$PATH
+
+install:
+  - yarn install --no-lockfile
 
 script:
   # 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
 
 before_deploy:
-  - npm install -g auto-dist-tag
+  - yarn global add auto-dist-tag
   - auto-dist-tag --write
 
 deploy:

config/ember-try.js

@@ -1,6 +1,7 @@
 /* eslint-env node */
 
 module.exports = {
+  useYarn: true,
   scenarios: [
     {
       name: 'ember-2.0',