MAINT: stats: Update ppcc_plot and ppcc_max docstring.
MAINT: stats: Update ppcc_plot and ppcc_max docstring.

* Use weibull_min instead of tukeylambda to generate
  the sample data.  This generates nicer plots in the
  ppcc_plot docstring, and ensures that boxcox_normplot
  is given valid data.
* Reduce the size of random sample from 10000 to 500; the
  smaller sample demonstrates the functions just as well
  as the larger sample.
* Add a histogram to the ppcc_plot example.
* Remove text from the ppcc_max docstring that was
  probably copy-pasted from the ppcc_plot docstring.
* Do some additional copy-editing of the docstrings.

zerothi/scipy,ilayn/scipy,scipy/scipy,matthew-brett/scipy,matthew-brett/scipy,andyfaff/scipy,scipy/scipy,anntzer/scipy,perimosocordiae/scipy,zerothi/scipy,rgommers/scipy,Stefan-Endres/scipy,Eric89GXL/scipy,grlee77/scipy,matthew-brett/scipy,Eric89GXL/scipy,andyfaff/scipy,endolith/scipy,matthew-brett/scipy,endolith/scipy,perimosocordiae/scipy,anntzer/scipy,WarrenWeckesser/scipy,perimosocordiae/scipy,tylerjereddy/scipy,andyfaff/scipy,e-q/scipy,tylerjereddy/scipy,ilayn/scipy,anntzer/scipy,scipy/scipy,andyfaff/scipy,tylerjereddy/scipy,ilayn/scipy,grlee77/scipy,perimosocordiae/scipy,vigna/scipy,zerothi/scipy,anntzer/scipy,rgommers/scipy,zerothi/scipy,WarrenWeckesser/scipy,Stefan-Endres/scipy,anntzer/scipy,andyfaff/scipy,mdhaber/scipy,matthew-brett/scipy,tylerjereddy/scipy,perimosocordiae/scipy,andyfaff/scipy,vigna/scipy,vigna/scipy,ilayn/scipy,tylerjereddy/scipy,perimosocordiae/scipy,WarrenWeckesser/scipy,mdhaber/scipy,WarrenWeckesser/scipy,scipy/scipy,mdhaber/scipy,Eric89GXL/scipy,WarrenWeckesser/scipy,rgommers/scipy,anntzer/scipy,grlee77/scipy,rgommers/scipy,grlee77/scipy,endolith/scipy,mdhaber/scipy,Stefan-Endres/scipy,WarrenWeckesser/scipy,vigna/scipy,Stefan-Endres/scipy,Eric89GXL/scipy,e-q/scipy,endolith/scipy,grlee77/scipy,scipy/scipy,endolith/scipy,rgommers/scipy,e-q/scipy,zerothi/scipy,e-q/scipy,mdhaber/scipy,Stefan-Endres/scipy,Eric89GXL/scipy,e-q/scipy,ilayn/scipy,ilayn/scipy,Eric89GXL/scipy,endolith/scipy,Stefan-Endres/scipy,zerothi/scipy,mdhaber/scipy,scipy/scipy,vigna/scipy