switch to struct initialiser; change latency to a time.Duration; add device relative support
Add Resume Support

Update the example to stop and restart the stream for testing.
Remove old FSEventsSince function because it was going stale.
Use the EventStream structure as the callback context so the current
EventId can be tracked (for resuming).
Add a Restart function that resumes the stream (potentially after
changes to the stream's parameters).
Add a sync parameter to the Flush function.
Add finalizer for safety

Update Stop to be 'safe' to call when the stream isn't started.
Add a finalizer to the Stream to protect against a panic when the stream
is freed while it's running. The finalizer stops the stream instead to
avoid the panic.

closes #3