Removed some debugging to std out, silenced pushd/popd operations;
added line to skip empty directories.

The first live test of this script ended with failures… Corrected the
script in some references of $1 which were being passed without quote
marks… Always use quote marks when handling user input! d'oh!

Also, there's a massive memory leak……. not sure where from though… all
the recursion? It seems to have eaten up 11 GB of memory and eaten into
the swap by ~250 MB over the process until I killed it 7 hours after
start...