readEvent() currently blocks.

See https://code.google.com/p/go/issues/detail?id=5536

@howeyc attempted to change this in 3bfa915 but reverted it 7beb451 due to reports of no new events howeyc/fsnotify#52.

This was something I added to stop readEvent from blocking forever.
Basically calling close would mean no new data came to the file descriptor
and Read would block forever.

This was an attempt to use select with a timeout so it would return after
the timeout stating whether there was new data.