New formula: cv-0.4.1

Homebrew formula for [BestPig/cv](https://github.com/BestPig/cv), which is an OS X-compatible fork of [Xfennec/cv](https://github.com/Xfennec/cv). It seems that eventually the fork is going to be merged into [Xfennec/cv](https://github.com/Xfennec/cv) but I dunno, the formula could probably be migrated to use that repo when that happens.

Ref Xfennec/cv#30, #Homebrew/homebrew-headonly#60.