More sleep() tests.
Exit when the main fiber ends, even if there are pending events.

Also, this now manages memory for waiting fibers.
Remove handle type from WaitingFiber since it's not used.
Get rid of old file IO code and using libuv.

You can now open and close files using libuv. Reading isn't
implemented yet.
Clean up file system request objects.
Remove completed events from the wait list.

Also cleaned up and shuffled some code around a bit.
Remove generated stuff from repo.