Stop hijacking escape key in normal mode

Fixes #1, Fixes #2, Fixes #3. Hijacking the escape key was a convenience that
caused more harm than good. Its only purpose is to clear out any lingering
cursors due to unexpected user commands. Pressing CTRL-N in normal mode should
do the same. Updated the doc to highlight this fact. In the future, we might
want to provide a command that explicitly calls reset()