 Shares of CarGurus Inc. CARG, -3.17 nosedived on Tuesday after the online platform for buying and selling cars reported third-quarter results that missed expectations and issued a forecast that came in well below expectations. CarGurus reported net income of 18.8 million, or 14 cents a share, compared with 29.3 million, or 24 cents a share, in the third quarter a year earlier. 