Twitter Inc (TWTR.N) said on Thursday the social media company is signing up users as quickly as most of last year after a fourth-quarter slowdown, boosting its shares 11 percent. Twitter beat Wall Street’s profit and revenue targets in the fourth quarter. User growth weakened in the quarter, but picked up in the new year, Chief Executive Dick Costolo said in a statement. Twitter added 13 million to 16 million users in each of the first three quarters of 2014 and was on track to hit a similar number in the current quarter, it said.