Holding that the immigration judge's adverse credibility determination was supported by substantial evidence; the immigration judge did not err by improperly discounting the Petitioner's corroborating evidence when denying his application for asylum; the immigration judge did not err, on remand, by conducting an additional hearing and taking oral testimony before denying Petitioner's application for asylum; and the immigration judge's determination that the Petitioner did not demonstrate a likelihood that he would be tortured if returned to Bangladesh was supported by substantial evidence.