Add rulers to codecells

gistfile1.js

// Add rulers to a codecell
//

define([
    'base/js/namespace',
    'jquery',
    'require',
    'base/js/events',
    'codemirror/lib/codemirror',
    'codemirror/addon/display/rulers'
], function(IPython, $, require, events, codemirror) {
    "use strict";
    if (IPython.version[0] < 3) {
        console.log("This extension requires IPython 3.x");
        return
    }

var nums = "0123456789", space = "          ";
var colors = ["#fcc", "#f5f577", "#cfc", "#aff", "#ccf", "#fcf"];
var rulers = [], value = "";
for (var i = 1; i <= 10; i++) {
    rulers.push({color: colors[i], column: i * 10, lineStyle: "dashed"});
    for (var j = 1; j < i; j++) value += space;
    value += nums + "\n";
  }
    
    var createCell = function (event,nbcell) {
        var cell = nbcell.cell;
        if ((cell instanceof IPython.CodeCell)) {
            cell.code_mirror.setOption('rulers', rulers);

        }
    };
    
    var cells = IPython.notebook.get_cells();
    for(var i in cells){
        var cell = cells[i];
        if ((cell instanceof IPython.CodeCell)) {           
            cell.code_mirror.setOption('rulers', rulers);
        }
    }

    events.on('create.Cell',createCell);
    
});