set CRAN URL via environment variable RTRAVIS_CRAN_URL, default http://cran.rstudio.com
set CRAN URL via environment variable RTRAVIS_CRAN_URL, default http://cran.rstudio.com

An "options" call is appended to `Rprofile.site` during bootstrapping

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