The leader of the agency charged with the ObamaCare rollout is stepping down after five years on the job. Marilyn Tavenner, administrator of the Center for Medicaid and Medicare Services (CMS), announced her departure Friday, which will take effect next month. "It is with sadness and mixed emotions that I write to tell you that February will be my last month serving as the administrator for CMS," Tavenner wrote in an email to staff. Tavenner is leaving after five turbulent years overseeing the agency. Her tenure included the disastrous rollout of the government’s HealthCare.gov website as well as, most recently,...