fix(build): bump AppVeyor to build with Node 6.9 from 4.2
fix(build): bump AppVeyor to build with Node 6.9 from 4.2

nylas/nylas-mail,simonft/nylas-mail,simonft/nylas-mail,nylas-mail-lives/nylas-mail,simonft/nylas-mail,nirmit/nylas-mail,nylas-mail-lives/nylas-mail,nylas/nylas-mail,nirmit/nylas-mail,nirmit/nylas-mail,nylas-mail-lives/nylas-mail,nylas-mail-lives/nylas-mail,nirmit/nylas-mail,simonft/nylas-mail,nylas/nylas-mail,simonft/nylas-mail,nylas/nylas-mail,nylas-mail-lives/nylas-mail,nirmit/nylas-mail,nylas/nylas-mail