use either /usr/bin/open or /usr/bin/xdg-open for sending e-mail when RStudio is active
extract function email_browser, use Sys.which
use early termination instead of deeply-nested if-s
import methods::setPackageName so test can be run easily with Rscript
Pass on auth_token. Closes #442
Merge pull request #444 from jlburkhead/master

import methods::setPackageName so test can be run easily with Rscript
Merge pull request #443 from krlmlr/email

use either /usr/bin/open or /usr/bin/xdg-open for sending e-mail when RStudio is active
Pass ncpus to install.packages.
Manual merge. Closes #401.