use ogg instead of mp4 for hook_ffmpeg_html()

for some reason, I cannot get mp4 to work under Ubuntu any more
use single quotes
fixes #535: for single-lettered pandoc arguments, the values are passed to them after spaces instead of equal signs

also solves the problem at http://stackoverflow.com/q/16569010/559676
news about the video (animations)
add @trevorld to contributors for #533
can merge two regexp patterns into one (#533)
add the `quiet` argument to knit2pdf() for #533, and the default compiler for rst documents is rst2pdf
roxygenize
bump version