Creating an installer (.pkg file) from the command line
I found an alternative, while not the most ideal, it does the job for me. It's using packagesbuild commandline that comes with Packages (http://s.sudre.free.fr/Software/Packages/about.html). It lets you create a .pkg file through the command line, but you need to create a .pkgproj file, which you create with the Packages application.