chore(travis): update to use node 4.x

Author: petebacondarwin

Diff for: .travis.yml

@@ -14,18 +14,20 @@ branches:
     - /^g3_.*$/
 
 env:
-  # - CXX=g++-4.8
   matrix:
     - JOB=unit BROWSER_PROVIDER=saucelabs
     - JOB=docs-e2e BROWSER_PROVIDER=saucelabs
     - JOB=e2e TEST_TARGET=jqlite BROWSER_PROVIDER=saucelabs
     - JOB=e2e TEST_TARGET=jquery BROWSER_PROVIDER=saucelabs
   global:
+    - CXX=g++-4.8  # node 4 likes the G++ v4.8 compiler
     - SAUCE_USERNAME=angular-ci
     - SAUCE_ACCESS_KEY=9b988f434ff8-fbca-8aa4-4ae3-35442987
     - LOGS_DIR=/tmp/angular-build/logs
     - BROWSER_PROVIDER_READY_FILE=/tmp/browsersprovider-tunnel-ready
 
+# node 4 likes the G++ v4.8 compiler
+# see https://docs.travis-ci.com/user/languages/javascript-with-nodejs#Node.js-v4-(or-io.js-v3)-compiler-requirements
 addons:
   apt:
     sources: