use "files" from package.json if CLI args don't specify file paths

[heartsucker]

This might be too annoying with all the white space problems that exist. Needs investigation.

[steevhise]

also or perhaps alternatively, can extra_files take a list of files rather than a directory? I have several loose files at root level, i'd rather specify them all in my package.json rather than have to list them all on the command line (or put them all in some directory.)