Other ergonomic feedback

[murphyke]

• Because of experience with zip or tar, I subconsciously expect this tool to accept an archive name followed by a list of files (or, if I'm lucky, accept a list of files on stdin if I do something special). I don't expect it to grab all .csv files in the directory.
• I definitely don't expect the tool to recurse into subdirectories to find files - could cause issues. E.g., it will cause error messages if somebody tries to pack into a subdirectory of the current directory.
• It is surprising (but not necessarily bad) to find a metadata.csv file created in the current directory separately from the created archive file (in a different directory, in this case).
• When I ran data-models-packer -out ~/tmp/out/packed.tar.gz ., the archive file was created, but when I tried to look at it with tar tvf ~/tmp/out/packed.tar.gz, I got gzip: stdin: not in gzip format.

[gracebrownecodes]

Changes:

1. Add functionality and known bugs sections from README to the usage message.
2. Allow for packaging into a file within the data directory?