code: function lowerCaseHeaders(headers) {
  	var res = {};
  
  	Object.keys(headers).forEach(headerName => {
  		res[headerName.toLowerCase()] = headers[headerName];
  	});
  
  	return res;
  }
docs: Given key-value set of HTTP headers returns the set with lowercased header names
  
  @param {object} headers
  @returns {object}