Update tests for `r_install` on multiple packages.

(Based on a comment from @krlmlr.)
Update `fakepackage`.
Tweak a test yet again.
Remove a currently broken test.

Something funny is going on here; I'm filing #41 to track it.
More tests in .travis.yml.

Fixes #41.
Merge branch 'master' into osx

Conflicts:
	.travis.yml