Use ace keybindings instead of onKeyDown

[pfgithub]

    <AceEditor
      ref="aceEditor"
      mode="sql"     // Default value since this props must be set.
      theme="chrome" // Default value since this props must be set.
      commands={[{   // commands is array of key bindings.
        name: 'removeline', //name for the key binding.
        bindKey: {win: 'Ctrl-X', mac: 'Command-X'}, //key combination used for the command.
        exec: 'removeline'  // name of the command to rebind
      }]}
    />