adding an apt-get wrapper
oops
adding a CRAN install step
adding a CRAN install step, typo corrected
simpler approach with explicit loop
additional tweaking

using adduser to staff group to write in /usr/local/lib/R/site-library
install just r-base-dev (which implies all the R build needs and more)
install littler which may come in handy for scripting
use chmod for now
a few more changes

- add travis user to group staff to permit sudo-less install.packages() in /usr/local
- generally less sudo use
- devtools install optional
- some reindation as my Emacs config like four spaces :)
Merge branch 'master' of https://github.com/eddelbuettel/r-travis into
merge-dirk

Merged Dirk's changes roughly verbatim, still need to test.

Conflicts:
	scripts/travis-tool.sh
Do a little tidying/normalization.

This does two things:
 * sets indentation to 4 (egads!)
 * makes devtools use uniform, with a note that it might be made optional.
Tweak Dirk's changes to get things passing again.
Add .Rbuildignore.

closes #22
Add notification info, restrict branch for build shield.
Add an apt package to our test package (for testing).

closes #14
do not hard-code the Ubuntu release name

can use `lsb_release -cs` instead
Installing R from a CRAN binary package instead of homebrew
Triggering a build with an edit of README
commented out OS X lines from .travis.yml so the build defaults to Linux
Merge pull request #25 from yihui/patch-1

do not hard-code the Ubuntu release name
Be nitpicky about $() vs backquote.