Fall back on AD?

This bit me today:
```julia
julia> with_logabsdet_jacobian(cbrt, 2.0)
NoLogAbsDetJacobian{typeof(cbrt), Float64}()
```

I could add a method for this, but there are so many other functions out there, maybe this could be automated?

This seems possible, since it's invertible:
```julia
julia> inverse(cbrt)
(::Base.Fix2{typeof(^), Int64}) (generic function with 1 method)
````
and AD-friendly:
```julia
julia> ForwardDiff.derivative(cbrt, 2.0)
0.2099868416491455
```