After multiple iterations over the past four and a half years, Twelve South has just introduced the biggest update to its BookArc lineup yet: wood. BookArc möd for MacBook ($80) takes the tried and true design and renders it out in one of three natural wood finishes. Twelve South, much like Apple, is all about evolution when it is successful in a product category. While a new material may not seem like a big deal, it’s a clear departure from…