convert to knitr; generated vignette differs, still need to fix that
change RStudio project to use knitr
avoid interpretation of code chunk syntax in example
format code chunks like in the original vignette

- don't print messages at all
replace tabs by spaces
require -> library
remove space at eol
Merge branch 'master' into knitr-vignette

Conflicts:
	GNUmakefile
	vignettes/tikzDevice.Rnw
building now works
change output back to tabs
install knitr for Travis-CI
ignore vignettes compiled locally [ci skip]
Merge pull request #37 from yihui/knitr-vignette

Use knitr for the vignette