Marvel is finally pushing ahead with the highly anticipated “Black Widow” standalone movie starring Scarlett Johansson, with Jac Schaeffer penning the script. Sources say this is still very early development, as the film has no greenlight, but naming a writer is the closest the studio has come to moving forward on a standalone pic. Marvel President Kevin Feige met with several candidates before tapping Schaeffer, and Marvel execs met with Johansson to discuss what they wanted from a “Black Widow” writer. Schaeffer is an up and coming scribe who broke out with her Black List script “The Shower,” a comedy...