Plays.tv now offers a Chrome plugin that allows the sharing of 30-second gameplay excerpts from Twitch streams that include full attribution for the original streamer and links back to the source. Here's word on how this works:

With the Plays.tv Chrome Extension, users can capture a 30-second, source-quality video clip of any Twitch livestream moment after it’s happened. The clip can then be trimmed and posted to Plays.tv – with one-click sharing to Reddit, Twitter, Facebook, etc. The video is posted with attribution to the original streamer; Twitch broadcasters will have all highlights from their Twitch stream presented on their Plays.tv profile page, organized by livestream session.