Attach a single keydown event per node

[danburzo]

I haven't tested the actual performance impact, but I believe there should be a single keydown listener per node that dispatches the various key events as needed. Judging from the TODO in the source, that was also the original intention.

I made a fork and I'm trying to come up with a solution, but I took the opportunity to create this issue as well, just in case anyone has specific ideas on how we could go about doing this.