chore(travis): enable native toolchain support

Author: dignifiedquire

.travis.yml

@@ -3,6 +3,7 @@ language: node_js
 node_js:
   - 4
   - 5
+  - stable
 
 # Make sure we have new NPM.
 before_install:
@@ -13,12 +14,20 @@ script:
   - npm test
   - npm run coverage
 
-addons:
-  firefox: 'latest'
-
 before_script:
   - export DISPLAY=:99.0
   - sh -e /etc/init.d/xvfb start
 
 after_success:
   - npm run coverage-publish
+
+env:
+  - CXX=g++-4.8
+
+addons:
+  firefox: 'latest'
+  apt:
+    sources:
+      - ubuntu-toolchain-r-test
+    packages:
+      - g++-4.8