Update resolver to 4.2
Update resolver to 4.2

This uses ghc 7.10.3 and works much better on osx
sdiehl/write-you-a-haskell,yupferris/write-you-a-haskell,sdiehl/write-you-a-haskell,FranklinChen/write-you-a-haskell,FranklinChen/write-you-a-haskell,yupferris/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,sdiehl/write-you-a-haskell,FranklinChen/write-you-a-haskell,sdiehl/write-you-a-haskell,FranklinChen/write-you-a-haskell,sdiehl/write-you-a-haskell,yupferris/write-you-a-haskell