Run tests on source version, not package version
Restore save of likelihood functions with mle output.
Updated mcmc to save the likelihood function with the samples.

Approximately the same interface as find.mle().  The function is saved
as "func", even though mcmc takes the argument "lik".  Not very pretty,
but I can't really change the argument names at this point.
Update the likelihood extraction functions (now exported as get.likelihood)
Update PGLS code to use saved likelihood functions.