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: Politico: "Erick Erickson...writes today that he's backing former GOP Gov. Mark Sanford" http://www.politico.com/blogs/charlie-mahtesian/2013/02/forgiving-mark-sanford-157040.html  Responser: This s the man we need in Washington.
