Added data URL support for node.js; (#4725)

* Added data URL support for node.js;
Added missed data URL protocol for the browser environment;
Optimized JSON parsing in the default response transformer;
Refactored project structure;
Added `cause` prop for AxiosError instance that refers to the original error if it was wrapped with `AxiosError.from` method;
Added fromDataURI helper;
Added test for handling data:url as an `arraybuffer|text|stream`;

* Added throwing of 405 HTTP error if the method is not GET;

lib/helpers/fromDataURI.js

@@ -0,0 +1,51 @@
+'use strict';
+
+var AxiosError = require('../core/AxiosError');
+var parseProtocol = require('./parseProtocol');
+var platform = require('../platform');
+
+var DATA_URL_PATTERN = /^(?:([^;]+);)?(?:[^;]+;)?(base64|),([\s\S]*)$/;
+
+/**
+ * Parse data uri to a Buffer or Blob
+ * @param {String} uri
+ * @param {?Boolean} asBlob
+ * @param {?Object} options
+ * @param {?Function} options.Blob
+ * @returns {Buffer|Blob}
+ */
+module.exports = function fromDataURI(uri, asBlob, options) {
+  var _Blob = options && options.Blob || platform.classes.Blob;
+  var protocol = parseProtocol(uri);
+
+  if (asBlob === undefined && _Blob) {
+    asBlob = true;
+  }
+
+  if (protocol === 'data') {
+    uri = uri.slice(protocol.length);
+
+    var match = DATA_URL_PATTERN.exec(uri);
+
+    if (!match) {
+      throw new AxiosError('Invalid URL', AxiosError.ERR_INVALID_URL);
+    }
+
+    var mime = match[1];
+    var isBase64 = match[2];
+    var body = match[3];
+    var buffer = Buffer.from(decodeURIComponent(body), isBase64 ? 'base64' : 'utf8');
+
+    if (asBlob) {
+      if (!_Blob) {
+        throw new AxiosError('Blob is not supported', AxiosError.ERR_NOT_SUPPORT);
+      }
+
+      return new _Blob([buffer], {type: mime});
+    }
+
+    return buffer;
+  }
+
+  throw new AxiosError('Unsupported protocol ' + protocol, AxiosError.ERR_NOT_SUPPORT);
+};