Use current LTS version of Node.js for travis
Use current LTS version of Node.js for travis

MissLoveWu/webvowl,VisualDataWeb/WebVOWL,VisualDataWeb/WebVOWL,MissLoveWu/webvowl,leshek-pawlak/WebVOWL,leshek-pawlak/WebVOWL