Minimal space usage (via flag or default)

[dgets]

At some point, implement a flag that will specify minimal space usage. It could be used in a variety of different circumstances that might occur in usage of this app; for instance, in the extraction of only a particular file, existing within a secondary sub-archive, it could ensure that only the correct archive tree is written to disk before recursion, as well as deleting sub-archives from disk after the correct contents are pulled from them.

Then again, maybe this is just a good default behavior... I think, at this point, that options for both would be good, as full expansion/extraction is a good default for testing purposes. We'll see what to do with it exactly when it's closer to a working program.