install binary R packages with just one apt-get install call -- again
install binary R packages with just one apt-get install call -- again

- otherwise the logs just look horrible: https://travis-ci.org/yihui/tikzDevice/builds/13447667, lines 365-700
- runtime penalty is substantial, too

craigcitro/r-travis,craigcitro/r-travis,qinwf/r-travis,hadley/r-travis,hadley/r-travis,robzhu/r-travis,qinwf/r-travis,eddelbuettel/r-travis,eddelbuettel/r-travis,robzhu/r-travis