don't restrict tests only to master branch; instead test all branches that don't end with -expt
Make the `.Rbuildignore` fanciness work with `set -e`.

I stupidly forgot that `$?` isn't something you can check with `set -e` -- if
it's on, you die before you check the previous result.
Merge pull request #43 from krlmlr/except-expt

don't restrict tests only to master branch; instead test all branches that don't end with -expt
comment on the restriction of tested branches
Merge pull request #45 from krlmlr/except-expt

comment on the restriction of tested branches
Add an RBinaryInstall command, and use it with c2d4u.

This patch does three main things:
 * add c2d4u to our apt configuration,
 * add a command to install a binary version of an R package from c2d4u, and
 * use c2d4u for devtools.

I also cleaned up one or two printed messages.
Convert r_binary_install arg to lowercase.
Add some fixes for OSX.
Update the test after updating the source. Classy.
Add multiple args for r_binary_install.
bash. yep.
bash. yep. again.
bash. yep. again. yet again.
Make a message more readable.
dumping test files if any
trying something else
one directory below
using a simpler cat now
Merge pull request #48 from romainfrancois/master

dump results of tests
Variable rename.