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
Merge remote-tracking branch 'hadley/master' into 549-r-appveyor

Conflicts:
	NAMESPACE