💚 Fix eslint install on Travis.ci

Author: welcoMattic

.travis.yml

@@ -2,15 +2,22 @@ language: node_js
 
 node_js:
   - 6
-  - 4
 
 before_install:
-  - yarn global eslint
+  # Repo for newer Node.js versions
+  - curl -sL https://deb.nodesource.com/setup_6.x | sudo -E bash -
+  # Repo for Yarn
+  - sudo apt-key adv --keyserver pgp.mit.edu --recv D101F7899D41F3C3
+  - echo "deb http://dl.yarnpkg.com/debian/ stable main" | sudo tee /etc/apt/sources.list.d/yarn.list
+  - sudo apt-get update -qq
+  - sudo apt-get install -y -qq yarn
+  - npm i -g eslint
 
 install:
   - yarn install --production
 
 cache:
+  yarn: true
   directories:
     - node_modules