code: function(slug, num_chars=2) {
          if(typeof slug !== 'string') throw new Error('slug must be a string');
          if(slug === '') throw new Error('slug cannot be an empty string');
          if(isNaN(Number(slug))) return slug;
          slug = slug.replace(/^(0+)/, '').trim();
          while(slug.length < num_chars) {
              slug = '0' + slug;
          }
          return slug;
      }
docs: NOTE: this method was taken from the resource-container module where it is thoroughly tested.
  
  Pads a slug to 2 significant digits.
  Examples:
  '1'    -> '01'
  '001'  -> '01'
  '12'   -> '12'
  '123'  -> '123'
  '0123' -> '123'
  Words are not padded:
  'a' -> 'a'
  '0word' -> '0word'
  And as a matter of consistency:
  '0'  -> '00'
  '00' -> '00'
  
  @param slug {string} the slug that wil be padded
  @param num_chars {int} the number of 0's to pad the slug with. Default is 2
  @returns {*}