jth_hess_coord! seems not implemented

[leonardosecchin]

An error occurs when calling jth_hess_coord!. This function appears not to be implemented in api.jl.

[abelsiqueira]

Indeed it isn't. It should be possible to implement it using cish, I think. Are you interested in working on that?

[amontoison]

Added in #352 and tested in #399.