fix #862: grepl() should have been grep()
add @dgrtwo to the list of contributors for #867, and add a news item
add a news item for #869 and @lq to the list of contributors
revert to highlight.js 7.3 because 8.0 leaves a large white margin at the bottom for unknown reasons
fixes yihui/knitr-examples#35: support chunk options in the R script for stitch()
Revert "Add to stitch() documentation that it doesn't support chunk options"

This reverts commit 405b415ed5c5108ce23da8c31de9e5d83f333bd0.
bump version