events: remove indeterminancy from event ordering

The order of the `newListener` and `removeListener` events with respect
to the actual adding and removing from the underlying listeners array
should be deterministic. There is no compelling reason for leaving it
indeterminate. Changing the ordering is likely to result in breaking
code that was unwittingly relying on the current behaviour, and the
indeterminancy makes it impossible to use these events to determine when
the first or last listener is added for an event.

PR-URL: https://github.com/iojs/io.js/pull/687


Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>