Squelch Zookeeper build "errors" that aren't errors from console.
Fix checkUp bug found by R CMD check.
Default of variable_importances changed.
Fix a bunch of documentation formatting issues for --as-cran.
Super strict --as-cran checker.

Jenkins wasn't catching stuff because R CMD CHECK --as-cran doesn't exit nonzero
when it should.
Bug in format string of package version error message.
Tweak example formatting to avoid --as-cran warning.
Some as.Date documentation fixes, but still isn't totally clean.
Merge branch 'master' into rel-lambert