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
Bump version to 1.5.0.9000
Add date to session_info()
Export print method & re-document
Added new check environment var

Via https://github.com/wch/r-source/commit/f49fe2834e7573571351c7784d3bed461d077645
Tease apart metadata creation from installation
Pull source_pkg into own function
Clarify download message
Pull download() and add_metadata() out of install_pkg
Update docs
Rename install_pkg to install_pkg
Add remote class & objects for github