Add id when reading many csv files

I have been thinking about this a little and have a few options for how a user might add an id to many files.

1) purrr::imap allows us to access id information if the object passed is a named list.
2) purrr::map2 would allows us to ingest two vectors of equal length, file.names and ids
3) other options

I do think we need this functionality at some point.