Added support for multiple input dirs and input archives

[marcellus-trixus]

Hi,
I am not sure if you want this change in your project, but I needed this for my use case and thought you might find it useful. It allows user to specify multiple input directories.

In my case it comes really handy as I warp my package very often and in parallel. I have a huge set of static assets and only a one or two files that are actually changing with each package. With this feature I am able to store static assets in a separate directory and just make a temp directory with a couple of (dynamic) files for each package I make. This saves me copying 100+MB each time I make a package.

[marcellus-trixus]

Hi,
I have added another possibly interesting feature - app argument to add already packed tgzs into the package. This saves makes the packaging process a lot faster (in my case went from 12 seconds to 0.5 second).