Enable C++-compatible compiler on travis. https://docs.travis-ci.com/user/languages/javascript-with-nodejs#Node.js-v4-(or-io.js-v3)-compiler-requirements

Author: iamdustan

.travis.yml

@@ -8,3 +8,12 @@ script:
  - npm run lint
  - flow check
  - npm test
+env:
+ - CXX=g++-4.8
+addons:
+ apt:
+ sources:
+ - ubuntu-toolchain-r-test
+ packages:
+ - g++-4.8
+