Force NVM 6

Author: BenFradet

.travis.yml

@@ -34,6 +34,9 @@ install:
 - gem install ruby_dep -v 1.3.1
 - gem install jekyll -v 3.4.3
 - gem install jekyll-redirect-from
+- nvm install 6
+- nvm use 6
+- node --version
 
 before_script:
   - sudo chmod +x /usr/local/bin/sbt