1.41 - maintenance and Chapter 6 revision

- added data(Dinosaurs) and its man page
- compare() defaults to WAIC now and displays stderr
- compare plot method contains more swag
- added ensemble() to construct ensemble predictions from WAIC/DIC
weights
- added mcreplicate() to multicore replicate using mclapply
- various man page updates to keep up with code
- fix for simulating from map models without linear models
- map2stan defaults to computing WAIC after sampling
- sim.train.test() added, with man page
- sim method for map updated to handle pointwise loglik for WAIC
calculation when ll=TRUE
- WAIC methods updated to perform pointwise calculations, allowing
computation of stderr and stderr of differences in WAIC