Minor fix for example demonstrating recursion
Minor fix for example demonstrating recursion

yupferris/write-you-a-haskell,FranklinChen/write-you-a-haskell,yupferris/write-you-a-haskell,yupferris/write-you-a-haskell,FranklinChen/write-you-a-haskell,FranklinChen/write-you-a-haskell,sdiehl/write-you-a-haskell,sdiehl/write-you-a-haskell,yupferris/write-you-a-haskell,sdiehl/write-you-a-haskell,yupferris/write-you-a-haskell,yupferris/write-you-a-haskell,FranklinChen/write-you-a-haskell,FranklinChen/write-you-a-haskell,FranklinChen/write-you-a-haskell,sdiehl/write-you-a-haskell,sdiehl/write-you-a-haskell,sdiehl/write-you-a-haskell