Merge pull request #577 from mingsnu/master

Add knit2rocco function
add library(knitr) to make sure the functions inside knitr will always be available

sometimes the user might not have loaded the knitr package: http://stackoverflow.com/q/17734135/559676
knitr-slides have been removed
use my style: single quote, wrap lines, 2 spaces indent, spaces around operators
rocco.css should not be placed under themes/, because themes/ is for syntax highlighting
example not satisfactory; will do it later
provide an HTML template for markdown so that we can use the template and stylesheet arguments

title and style are no longer necessary because they are present in markdownToHTML()
the background div does not work well when there is graphics output
make sure images in docs are not too wide
no margin for container; width of docs/code: half and half (important when there are plots)
add Weicheng Zhu @mingsnu to contributor list for #577
add a reference to Docco in rocco()
news about #577
roxygenize
bump version
use cellspacing 1 (thin horizontal lines between code blocks)
move generator to the meta tag so it is not too intrusive
rely on grep instead of ==
a dark trick to make sure the pre blocks will end up in the same cell
largely rewrite docAdjust() so that if there are images output from the code blocks, they will be moved up (then the plots and code will sit side by side)

besides, the pilcrows are added to all the rows now