Update the README
Update the README

- Removes the incubation line (already graduated)
- Go 1.5 is 3 years old. Remove not regarding building on 1.5
- Remove not working Slack widget

surajnarwade/kompose,skippbox/kompose,kadel/kompose,kubernetes/kompose,surajnarwade/kompose,kadel/kompose,skippbox/kompose,surajnarwade/kompose,cdrage/kompose,procrypt/kompose,cdrage/kompose,procrypt/kompose,skippbox/kompose,kubernetes/kompose,procrypt/kompose