per suggestion of @kohske and @ramnathv, use a chunk option `collapse = TRUE` instead of render_markdown(merge = TRUE)
roxygenize and bump version
remove NEWS from GIT
hardcode the filename for NEWS
even if the dev is not pdf, still try to pass dev.args to the device, e.g. pointsize is a shared argument of pdf() and png()

this fixes http://stackoverflow.com/q/21613467/559676 reported by @kbroman
it seems there is something wrong with travis today; try the dumb `apt-get update` approach
I do not think Michael Rutter has been maintaining the rdev ppa; it is still R 3.0.1 there
I do not think this would be an FAQ any more. In the spirit of "FAQ's are almost bugs", let me remove this "Infrequently Asked Question"
bye-bye, wrap=FALSE, you are a first-class citizen now :heart:
from @kbroman's example, I realized that the pipes did not work in markdown tables, and they have to be escaped to the HTML entity &#124;

see kbroman/knitr_knutshell#1
use the argument quiet = TRUE instead of setting opts_knit$set(progress = FALSE)
allows `r expression` for asciidoc input as well

this should solve @kohske's problem in #510
create dir for tikz output in the tikz engine, per suggestion of @kohske in f9d42dd7487
use @export instead of @S3method for the next version of roxygen2
closes #733: make the hook name accessible inside the hook function

all arguments of a hook function are optional now

this should close rstudio/rmarkdown#17 as well, because when hook is a character string, I will get() it
pass the encoding argument from knit2html() to markdownToHTML(), which requires markdown 0.6.5

rstudio/markdown#50 @kohske
more Rd changes from roxygen2 4.0
add fig.retina to opts_chunk and default to 1
add collapse = FALSE to opts_chunk
equivalently, use local({}) instead of (function(){})()