Use newer GCC

See nodejs/nan#435

.travis.yml

@@ -7,6 +7,13 @@ node_js:
 sudo: false
 addons:
   firefox: "34.0"
+  apt:
+    sources:
+      - ubuntu-toolchain-r-test
+    packages:
+      - g++-4.8
+env:
+  - CXX=g++-4.8
 notifications:
   email:
     on_success: never