add heuristic parameter initialization for parallel tempered sampler
add heuristic parameter initialization for parallel tempered sampler

dannygoldstein/sncosmo,kbarbary/sncosmo,sncosmo/sncosmo,sncosmo/sncosmo,dannygoldstein/sncosmo,dannygoldstein/sncosmo,kbarbary/sncosmo,kbarbary/sncosmo,sncosmo/sncosmo