Out of space errors

This MR addresses #20 (closed)

Basically, I added a custom except hook to handle uncaught exceptions. I have pretty high confidence that this code works even if an IOError is raised in the exitfuncs section. The custom excepthook calls sys.exit(1), which does not in turn retrigger calling the exitfuncs. If it did, the program could potentially never exit because the failed exitfunc would keep getting called, handled, and retried.