Update setup.py

Missed out on the `description` string in `setup.py`
Merge pull request #2 from lowks/patch-1

Update setup.py
Added cab files
Added .ar archives.
Added mimetype for tarballs
Added better error messages for failures and fixes a cleanup bug.
Added explicit unpacker selections.
Update unp.py

typo ?
Merge pull request #3 from lowks/patch-2

Update unp.py