Add missing call to file.path

see https://github.com/hadley/devtools/commit/44c247231622231c6611a7bfa0a4ed2ae5289c95#commitcomment-6867162
Merge pull request #515 from krlmlr/patch-2

Add missing call to file.path
load_all: Re-export imported objects. Fixes #518
Add tests for re-exporting imported objects
The R CMD option rebuild vingettes has been renamed build vingettes
Merge remote-tracking branch 'upstream/master'
Merge pull request #521 from statwonk/master

The R CMD option rebuild vingettes has been renamed build vingettes
Set github_url to API v3 redirect

Doesn't work yet. Old-school archive/master.zip redirect still does.
Merge remote-tracking branch 'upstream/master'