adding Handlebars helpers in a Rendr app

app.js

//the client app.js file
var //...
    // register your helpers (my method doesn't return anything, so the assignment is unnecessary)
    HandlebarsHelpers = require('../assets/handlebars/helpers').registerHelpers();
    //...

Gruntfile.js

// ...
    rendr_stitch: {
    // ...
        files: [{
          // ...
          src: [
            // ...
            // add your handlebars helpers to the src array to be stitched
            'assets/handlebars/*.js'
          ]
        }]
      }
    }

handlebars_helpers.js

// a file with some helpers, written in the style of the rendr-handlebars/shared/helpers.js file
var rendrHandlbars = require('rendr-handlebars'),
    S = require('string');

function helpers(Handlebars, getTemplate) {
  return {
    slugify: function(str, block){
      return S(str).slugify().s;
    }
  };
}

exports.registerHelpers = function registerHelpers() {
  rendrHandlbars.registerHelpers(helpers);
};

some_template.hbs

<a href="/{{slugify name}}">
    {{name}}
</a>