Definition: Given a 'poster' sentence and a corresponding 'response' (often, from Facebook or Reddit)classify the sentiment of the given response into four categories: 1) Positive, 2) Negative, 3) Neutral, and 4) Mixed if it contains both positive and negative.
Input: Poster: http://www.theborneopost.com/2013/06/03/us-women-on-nine-year-grand-slam-high/  Responser: I'm so happy for you, Sloane, Jamie, and Serena!
