code: function(envelope) {
  		var filePath = this._getFileName(envelope)
  
  		filendir.writeFile(filePath, JSON.stringify(envelope), function(err) {
  			if (err) {
  				log('File could not be saved in ' + this.config.cacheDir)
  				throw err
  			}
  		}.bind(this))
  	}
docs: Save request to file
  @param	{object} envelope
  @return {none}