Fix travis to use next version of npm
Fix travis to use next version of npm

npm 2.7.5 apparently broke something with node 0.8.
Need to use 2.7.6 for the time being

https://github.com/npm/npm/issues/7849

sendgrid/sendgrid-nodejs,sendgrid/sendgrid-nodejs,metaraine/sendgrid-nodejs,XEuRoMAN/sendgrid-nodejs,sendgrid/sendgrid-nodejs,vermaslal/sendgrid-nodejs