Don't attempt to remove path extension if the object is a folder.
Merge pull request #5 from lgarron/folder

Don't attempt to remove path extension if the object is a folder.
Merge pull request #3 from quicksilver/zip

Use UTIs
7z support.
Merge pull request #4 from lgarron/master

7z support.
Use the file extension/description instead of UTI for the compression obj name:
Use ARC and some DRY cleanup
Add tbz2 details to the docs
Remove Autorelease statements/NSLogs