added a regression test for the bug when a S4 is exported by a pkg loaded with load_all(, export_all = FALSE), then imported by another pkg. Also provided a (possible) fix for the bug based on base::loadNamespace()
include arguments to install_github and SHA1 in DESCRIPTION file
Merge pull request #349 from hadley/feature/install-github-sha1

Include arguments to install_github and SHA1 in DESCRIPTION file
implemented Winston's suggestions
Merge pull request #334 from kforner/s4exportbug

regression test + possible fix
Tweak news formatting
Update docs
Improve local docs. Closes #347
Make release smarter.
Closes #340
Fix dumb typo
Fix context name. #351
Use rstudio::previewRd, if available.
Closes #322
Update news
Respect getOption('unzip').
Closes #326
Relax description requirements.
Closes #351
Remove unnused vignettes
Improvements to source_gist.
Fixes #348
Remove incorrect statement from docs
Add check_dir argument to check().
Fixes #337
Build vignettes even when local = TRUE.
Closes #344