someone asked me for the donation link; here it is
remove run_chunk() since it is no longer useful due to ref.label and <<>>
for R 3.0.0, we can specify the vignette builder in DESCRIPTION and register the builder functions through tools::vignetteEngine()
for a vignette to be compiled through knitr, we need \VignetteEngine{knitr}
update Makefile for backward compatibility: if R version < 3.0.0, still run knit2pdf() manually
bump version