docs: function include(filePath, extraVars) {
      if(!pathIsAbsolute(filePath)){
        filePath = path.resolve(path.dirname(this.file), filePath);
      }
  
      var vars = {};
      for(var ii in this.vars){
        vars[ii] = this.vars[ii];
      }
      if(extraVars){
        for(var jj in extraVars){
          vars[jj] = extraVars[jj];
        }
      }
      return render(readFile(filePath, {encoding: 'utf8'}), vars, filePath);
    }