forward-compatibility with R 3.0.0 (should build Markdown vignettes under R 2.15.2 too so you won't get Ripleyed)
ignore the Makefile under the root directory; it is for my own use only
start version 1.2, and remove hook_rjournal()
roxygenize
knit_global() returns the global environment if not called inside knit()
run_hooks() uses the knitr global environment by default
closes #483: chunk hooks are run even when engine is not R
bump version