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 they key-bindings.zsh file
and removing edit-command-line.zsh.
Merge pull request #513 from randy909/fix-edit-cmdline

Fix edit-command-line binding