Improved clarity for Advanced Data vignette

[cherz4]

Based on comment in PR #6 , #6 (comment)

To improve clarity and understanding for the reader of the Advanced Data vignette, could you address the following?

1. In Treat it as non-extinct section, you refer to chainsR package, when I think you mean to refer to nbbp
2. You may wish to link to some Stan documentation on what divergences mean and when some amounts of divergence are reasonable or unreasonable. I am familiar with divergences, but the Stan message in your vignette is not the same as the one I worked with before (e.g. X # divergent transitions after warmup: How to Diagnose and Resolve Convergence Problems – Stan)
3. Can you explain / point out where you got the probability of 7% in the Comparison section more clearly?