chore(travis): change travis config to use modern compiler

Author: wzrdtales

.travis.yml

@@ -39,8 +39,16 @@ cache:
     - node_modules
 
 addons:
+  apt:
+    sources:
+      - ubuntu-toolchain-r-test
+    packages:
+      - g++-4.8
   mariadb: "10.0"
 
+before_install:
+  - export CXX=g++-4.8; export CC=gcc-4.8;
+
 before_script:
     - until nc -z localhost 27017 ; do echo Waiting for MongoDB; sleep 1; done
     - mysql -e "create database db_migrate_test;"