1.53 - Struwen Day Edition

- man page for dlkjcorr
- added rlkjcorr function (Ben's code)
- ensemble optionally ignores link or sim
- map() now catches another corner case in linear model definitions
- map2stan plot() method for traceplots now has window and n_cols
arguments
- added divergent(), which counts number of divergent iteration in
map2stan fit. Automatically warns user.
- map2stan better handles missing values in outcome variables. Working
towards automatic prediction interface through this method.
- some file rearrangement for sanity
- precis() checks and warns about divergent iterations
- minor updates to README