Make knitr and R dependencies explicit
split knit_bootstrap into two functions, knit_bootstrap_Rmd and knit_bootstrap_md, to put the bootstrap styles around a R markdown and knitted markdown file respectively. This allows knit_bootstrap_md to be used as a drop in replacement for markdownToHTML. Previous behavior of knit_bootstrap function is unchanged.
fix #9, wrong url in DESCRIPTION
change to using package layout so framework can be bundled as an R package.
implement knit_bootstrap function so external makefiles are no longer necessary to change styles or include the style choosers.
fix pre code issue with render_markdown in newer versions of knitr