Higher-order functions for zeit/micro

• compose() - because it should be a part of es6 right
• respondToLivenessProbe - to respond to k8s liveness probe with {"healthy": true}
• parseJSONInput - puts input json on req.json

Example:

const cmd = input => ({
  hello: input.world
})

module.exports = compose(
  respondToLivenessProbe,
  parseJSONInput,
  process.env.NODE_ENV !== 'production' && visualize
)(async req => cmd(req.json))

• curl localhost:3000 -> returns {"healthy": true}
• curl -XPOST -d'{"world": "world!"}' http://localhost:3000 -> returns {"hello": "world!"}