increase evaluate version dependency for #582
update bib
involve is a transitive verb
replace " with "{} to make sure " does not induce an umlaut: http://stackoverflow.com/q/18125539/559676
roxygenize
bump version
if hash is not character, cache does not exist
cosmetic
cache$output() does not check if the cache object exists, just load it with the expected mode

because I will check cache$exists() before loading it; this should not be a problem unless the user did something really bad (e.g. hacked the cache database)
closes #396: cache = 0, 1, 2, 3 for different levels of cache

I think this also closes #536
bump version; prepare CRAN release now
update evaluate and knitr versions
narrower code in the example knitr-twocolumn.lyx
a better example for the code width problem
the target vignettes should depend on the two lyx files
tweak knitr-intro
make news
Bears!!

Greg @gfinak said this would be my last GIT commit message if I push to Github in Alaska, since I'll be there for vacation for the next week. Let's see if he is right. I hope not, of course.

Anyway, this is knitr v1.4, and I start to pray CRAN masters won't bite me. Well, it is way better for them to bite me rather than bears biting me in Alaska.
code changes should invalidate cache (fixes an issue when cache<3)
Merge pull request #587 from knokknok/master

code changes should invalidate cache (fixes an issue when cache<3)