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: You are invited to join me and special guest General Stanley McChrystal for a free public event in Peabody on Monday: http://www.sethmoulton.com/meetmcchrystal  Responser: Hey, maybe if we listen to each other a little bit, we could learn something!
