reads from stdin and execute a callback `cb` passing the the content as param
function readFromStdin(cb) {
    var chunks = []
    var stdin = process.stdin
    stdin.resume()
    stdin.setEncoding('utf8')

    stdin.on('data', function (chunk) {
        chunks.push(chunk)
    })

    stdin.on('end', function() {
        cb(chunks.join(' '))
    })
}