Not satisfied with merely “nailing the number”, Goldman Sachs’ David Kostin forecasts the S&P 500’s trajectory through 2015. Recognizing, as we did, that Bullish Sentiment is as highs as it gets, Kostin expects short-term weakness during the next month (the drop), earnings growth thanks to lower oil prices into mid-year (the pop), but multiple compression after rate hikes into year-end (the slop)…