use g++4.8

Author: alsotang

.travis.yml

@@ -1,12 +1,30 @@
 sudo: false
+
 language: node_js
+
+env:
+  - CXX=g++-4.8
+
 node_js:
   - '0.10'
   - '0.12'
   - '4'
+
+addons:
+  apt:
+    sources:
+    - ubuntu-toolchain-r-test
+    packages:
+    - g++-4.8
+
 services:
   - mongodb
   - redis
 
+before_install:
+  - $CXX --version
+
 script: make test-cov
+
 after_success: cat ./coverage/lcov.info | ./node_modules/coveralls/bin/coveralls.js
+