Merge pull request #13 from Turbo87/yarn

CI: Use yarn instead of npm

.travis.yml

@@ -12,8 +12,7 @@ addons:
   chrome: stable
 
 cache:
-  directories:
-    - $HOME/.npm
+  yarn: true
 
 env:
   global:
@@ -35,9 +34,11 @@ 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 --non-interactive
 
 script:
   # Usually, it's ok to finish the test scenario without reverting

config/ember-try.js

@@ -1,5 +1,6 @@
 /* eslint-env node */
 module.exports = {
+  useYarn: true,
   scenarios: [
     {
       name: 'ember-lts-2.8',