Reads and understands TAR files.
Can handle string in memory, IO object, or file path.

I do plan to add write and modify capabilities to this, but I'm in no rush.

The main reason I wrote this is because I'm planning a webservice that will
receive tar files and parse their contents in memory.

This should work with all versions of ruby, but I've been developing and testing with:
ruby 1.8.7 (2010-01-10 patchlevel 249) [i486-linux]