Remove parenvs, since it has been moved to the pryr package
Rewrite function without parenvs
Remove more uses of parenvs in tests
Move in some sha extraction code
Extract union_write out of add_build_ignore
Improvements to use_rcpp. #548
Rename add_build_ignore to use_build_ignore.
Make pkg argument last argument
Add github user/repo to session_info()'s output
Recognize Bioconductor packages in session_info()

These packages _must_ have a 'biocViews' field in
DESCRIPTION, according to the How-to at
http://www.bioconductor.org/developers/how-to/biocViews/
Merge pull request #555 from gaborcsardi/fix/session-bioc

Recognize Bioconductor packages in session_info()
Merge pull request #554 from gaborcsardi/fix/session-github-repo

Add github user/repo to session_info()'s output
Don't try to export missing objects
Add test for missing exports
Add warning for missing exports
Update NEWS
Use write_dcf in create
Fix thinko. Closes #556
Fix missing export test
Update test to use bitops instead of removed splines package
Also check imports env for exports