Prot # GS-US-196-0123: A Phase 2b, Randomized, Double-Blind, Placebo-Controlled Trial Evaluating 16 and 24 Weeks of Response Guided Therapy With GS-9190, GS-9256, Ribavirin (Copegus) and Peginterferon Alfa 2a (Pegasys) in Treatment Naive Subjects with Chr