option to expand an epub

Low priority feature request to add the option to blow up an epub to an 
expanded directory, to complement the existing functionality to zip a directory 
up.

With amateurs making EPUBs using not-always-perfect conversion tools, it's not 
that uncommon to get errors that are not hard to fix but that requiring 
explaining the need to unzip the publication first. I was thinking it would be 
helpful if epubcheck could do both steps, so that the process could be 
simplified to using one program.

Thinking a simple option like:

-unpack <dir>

that if set would override any validation steps and simply unzip the epub to 
the specified directory.

Original issue reported on code.google.com by mgarrish on 25 Jun 2013 at 12:46

andreareider / epubcheck

option to expand an epub #286