one more test case for yihui/knitr#588
some test cases for numeric warning/message values; yihui/knitr#590
a test case for the new option results='hold'; yihui/knitr#593
examples for stitch()
smaller code width
" is "{} in messages now
changes in ggplot2
highr can keep blank lines now
due to the bug fix in highr, comments are correctly highlighted now
make
no need to call dep_auto() any more; autodep=TRUE is smart enough now
an example for Michael Friendly: move code out of the floats