gofmt myvarint.go
add myPostingLast

This is useful for copying an entire posting list such as when merging
multiple index files into a new one.
add Concat() to merge two disjunctive index files
add ConcatN() to merge many disjunctive index files
change index.AddFile() to return errors instead of logging them
add dcs-package-importer

This is not done/sufficiently tested, but the idea is to incrementally
update an index by incurring the 2x storage cost.
update .gitignore to ignore binaries