Untar source pkgs into unique dir, and unlink

Source packages were previously extracted directly into the tempdir(),
which could be problematic if directory names collide. Also unlink was
called non-recursively.

These problems are exacerbated if you try to install source packages
where the contents of the package are directly in the root, instead of
having a folder like $packagename wherein the package contents live.
This isn't common but is valid and breaks devtools if you try to install
>1 of these during the same R session.
Remove more uses of :::
Really major typo
fix trivial typo
Merge pull request #371 from krlmlr/trivial

fix trivial typo
Update NEWS
Merge pull request #368 from jcheng5/master

Untar source pkgs into unique dir, and unlink
Add roxygen3 support
Use roxygen2 3.0
Expore install_deps()
Update news. Remove roxygen2 version dep from DESC
Enable travis
Can't install all suggested packages on travis
Install binary version of XML package
_R_CHECK_FORCE_SUGGESTS_ needs to be false
Add build shield to readme
Don't try and clear caches for roxygen2 3.0
Don't include NEWS.md because CRAN hates extra files
Bump version for development
Add information about updating devtools