Fix edit-command-line binding

This binding doesn't work when the edit-command-line.zsh file is loaded
after the key-bindings.zsh file because 'bindkey -e' in key-bindings.zsh
resets the binding. Moving the bindings to the key-bindings.zsh file
and removing edit-command-line.zsh.

edit-command-line.zsh was introduced recently, #479 14 days ago