SAN FRANCISCO (Reuters) – Twitter Inc reported anemic user growth during the final three months of 2013, sending shares sinking after its first quarterly report as a public company. Shares dropped more than 10 percent to $58 in after hours trading. The company reported robust made $243 million in revenue during the fourth quarter, topping investors expectations of$218.2 million, on average. But user growth, a closely watched metric, appeared to falter. It averaged 241 million monthly users, up just 3. …