title: change thickness median line geom_boxplot()
body: <p>I want to do some modifications of a geom_boxplot(). Because my boxplots are really "small" sometimes (see yellow and green clade in the graphic <a href="https://www.dropbox.com/s/tnki63b7bofvz8b/boxplot.png">here</a>) i want to highlight the median even more. so is it possible to adjust the thickness of the median line?</p>