fixes for feedback method
add info method to all samplers
mh: always use (rerun) to initialize

No other transition type should have to worry about
handling a no-choice-available case.
fix slice sampler for integer dists
clip slice bounds to support, improve error messages
improve errors
only warn about out-of-range once
added vprintf, more consistent debugging output
update observe tests to run
slice, enumerative-gibbs error on structural choice
update and expand asia tests
more tests
fix verbose printing for observe
fixed slice sampler

The previous version was only correct for unimodal
posterior distributions. This version actually implements
the slice sampling techniques from Neal's paper.
slice sampler: added small-dist optimization
delete bogus slice-adjust dist method
remove enum-importance-sampler
update some documentation wording
add shape-generic mean