Talk ratings/suggestions

[Urigo]

Ability to post ratings and suggestions to the talks and speakers
maybe could even be private so it would be shared just with the speakers if they prefer for it not to be public

[martinbonnin]

+1 to private feedback. This isn't cool for anyone to have a talk downvoted publicly.

FWIW, the API is there. We'll need an UI for this. It's in the stretch goals but no promises.