npm install + git add -a

node_modules/axios/lib/helpers/normalizeHeaderName.js

@@ -0,0 +1,12 @@
+'use strict';
+
+var utils = require('../utils');
+
+module.exports = function normalizeHeaderName(headers, normalizedName) {
+  utils.forEach(headers, function processHeader(value, name) {
+    if (name !== normalizedName && name.toUpperCase() === normalizedName.toUpperCase()) {
+      headers[normalizedName] = value;
+      delete headers[name];
+    }
+  });
+};