Make 'export' work

[ewindisch]

This commit allows 'iopipe export --name bob X Y Z' to create an npm package in exports/bob which may be used to import and run an iopipe pipeline via node.

$ iopipe export --name hnstories HNtopstories
$ npm install exports/hnstories
$ node <<EOF
var hnstories = require("hnstories")
hnstories(function(output) {
 console.log("The top HN stories are: " + output)
})
EOF