Mapped vim bindings (j/k) to prev/next and space to next

- Mapped j/k down/up vim bindings to next/prev because muscle memory
- Mapped space to next because it's a large, easy-to-hit button, and
  it's default behavior is to go down anyway, which would throw off
  the alignment.
- Added `preventDefault` call on the event so that default up/down/space
  behavior wouldn't affect the alignment