Tonight’s episode four of Fargo was the last one sent out for preview by FX – and kept up the impressive streak in which each installment was even better than the one before. In particular in this episode, both Billy Bob Thornton and Martin Freeman, in their respective roles, get to shine by playing markedly against their established characters. Freeman, by being more forceful and menacing – and Thornton, by being comically less so. But for a very good, and sly, reason…