code: function toAbsolute(_href, dir, outdir) {
      if (isExternal(_href) || isDataURI(_href)) {
          return _href;
      }
  
      outdir = outdir == undefined? dir : outdir;
  
      _href = normalize(_href);
      dir = normalize(dir);
      outdir = normalize(outdir);
  
      // Path "_href" inside the base folder
      var hrefInRoot = normalize(path.join(dir, _href));
      if (_href[0] == '/') {
          hrefInRoot = normalize(_href.slice(1));
      }
  
      // Make it relative to output
      _href = path.relative(outdir, hrefInRoot);
  
      // Normalize windows paths
      _href = normalize(_href);
  
      return _href;
  }
docs: Convert a relative path to absolute
  
  @param {String} href
  @param {String} dir: directory parent of the file currently in rendering process
  @param {String} outdir: directory parent from the html output
  @return {String}