truncnorm is a package dependency

The new nonlinear logit code uses this package.
However, the next version will not.
nonlinear: prepare for hybrid monte carlo

The old apparently working function will be left in place with the
.AlbertChib suffix.  The function to be revised is a copy of the old
one, except I already deleted an incorrect comment.
nonlinear: confirm correct derivative calculation

analytic and numeric derivatives agree well
This still has breakpoint; the code after the breakpoint was not
intended to run
nonlinear: hybrid monte carlo first crack runs but no good

Use HybridMC package, though run into problems with passing arguments,
both it seeing the logDens dLogDens functions in mice and getting other
arguments that are passed in.
Also, HybridMC does not seem to have good defautl arguments; I had to
specify a lot of things explicitly.
It runs, but the resulting "chain" is constant.  Guesses along the way
include wild tau values.  Possibly every candidate point is rejected at
the metropolis steps.