Added support for automatic object serialization to FormData if `Content-Type` is `multipart/form-data`;
Added support for FormData to be overloaded using `config.env.FormData` option;
Added support for FormData in node.js environment through `form-data` package;

Added tests for FormData payload;

Refactored cancellation section;

…rmData

� Conflicts:
�	lib/defaults.js

Expose toFormData helper as a static method;
Refactored transform request;
Added kindOf, kindOfTest, endsWith, isTypedArray util;
Refactored utils.js to use kindOf for tests;

…ormData

� Conflicts:
�	lib/adapters/http.js
�	lib/defaults.js
�	lib/helpers/toFormData.js
�	package-lock.json
�	test/specs/helpers/toFormData.spec.js

# Conflicts:
#	package-lock.json
#	package.json

Added support for automatic object serialization to FormData if `Content-Type` is `multipart/form-data`;
Added support for FormData to be overloaded using `config.env.FormData` option;
Added support for FormData in node.js environment using `form-data` package;

(cherry picked from commit 73e3bdb)

… Form;

Added ability to submit FileList object as a FormData;
Updated README.md;