Merge pull request #17 from alang9/master

I broke hessian =(
Get rid of Lifted typeclass by introducing Domain type family

hessianF previously only required Num a, but now requires Floating a
conjugateGradientDescent and conjugateGradientAscent previously only required Fractional a but now requires Floating a
Merge branch 'monomorphize' of https://github.com/alang9/ad
major version bump
CHANGELOG entry for @alang9's refactoring
{Domain => Scalar}
First non-AD-based AD mode: Forward
Reverse mode
Use derived Typeable/Data when possible

This is possible as of GHC 7.7.
benchmark: Calculate BSM greeks