Update to newest npm in appveyor builds
Update to newest npm in appveyor builds

rajzshkr/bower,bower/bower,DrRataplan/bower,Blackbaud-EricSlater/bower,prometheansacrifice/bower,watilde/bower,Jinkwon/naver-bower-cli,thinkxl/bower,rlugojr/bower,pertrai1/bower,gronke/bower