changes default face color in violins, see discussion in #1226
add notebook with options, including those introduced in #1861
no unit tests yet
no change in bandwidth options as in #1226
REF: graphics violin_plot change face color, see #1226
DOC: add ipython notebook for boxplots
rebased, merge when TravisCI is green
Coverage remained the same when pulling 0f60867 on josef-pkt:doc_beanplot into 1c54d66 on statsmodels:master.