Fix .travis.yml so node 4.1 can use g++ for native compile.
Fix .travis.yml so node 4.1 can use g++ for native compile.

hawkular/hawkular-charts,mtho11/hawkular-charts,mtho11/hawkular-charts,hawkular/hawkular-charts,mtho11/hawkular-charts,hawkular/hawkular-charts