Rename “semantic callbacks” to just “callbacks?”

[Mr0grog]

When I first looked at this, I wondered for a brief moment what “semantic” callbacks were supposed to be. Maybe it would be simpler to just say “callbacks.” Barring that, “simple callbacks,” “Node.js-style callbacks,” or “plain callbacks” all seem like they might be a little more straightforward than “semantic.”

[rosshinkley]

Fair enough. "Callbacks" is probably enough. Consider it done.