add vi-like-bindings

[danner26]

bchao1#21 was prematurely closed. bchao1#23 implemented a vehicle for allowing multiple keys to be registered to the same method, but did not actually add the vi-like bindings that were requested in Issue bchao1#13

This branch actually implements the feature requested. Thanks @rcfox for bchao1#23 making it way simpler.

bchao1#24