Implement SEFD and JIKL setup keybindings

[baogorek]

Per @johncmerfeld's comments in Pull Request 11, which were

"I've got some thoughts on the user experience of scrolling; more specifically the keybindings. My intuition is that we could switch from the Vim keybindings to an SEFD and JIKL setup (right hand scrolls the current window, left hand can modify it – both hands mimic the arrow key structure and neither hand has to move from its natural typing position)."

We need to provide the ability to switch to those keybindings as part of this issue. It should be a simple switch (say by modifying a keyword argument). We may want to implement the full config file functionality with this issue.