It’s enough of a challenge to launch a new subscription movie channel in an industry segment dominated by the likes of HBO and Showtime. However, Epix, which begins life Friday, starts its adventure with a double feature of sorts: It will also offer a Web streaming version of its channel. That means Epix’s Chief Digital Officer Emil Rensing will have a busy Halloween, making sure the user experience for those potential paying customers will be more treat than trick as they seek other alternate forms of entertainment on their PCs.