add an 'inline' argument to spin() to allow inline R code; closes #620
document the 'inline' argument and roxygenize
should not delete the Rmd file; we need it for version control purposes
bugfix: regular expression for code detection
add example for false positive of detection of ((code))
ignore generated .tex and .sty files for examples
use more robust syntax {{code}}, ignore braces inside code
update (()) to {{}} in news for #620