Add mit license

Author: xJkit

LICENSE

@@ -0,0 +1,22 @@
+
+The MIT License (MIT)
+
+Copyright (c) 2018 Jay Chung
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.

README.md

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 > A save reminder component for react router v4.
 
-[![NPM](https://img.shields.io/npm/v/react-goodbye.svg)](https://www.npmjs.com/package/react-goodbye) [![CircleCI](https://circleci.com/gh/xJkit/react-goodbye/tree/master.svg?style=shield)](https://circleci.com/gh/xJkit/react-goodbye/tree/master) [![Coverage Status](https://coveralls.io/repos/github/xJkit/react-goodbye/badge.svg?branch=master)](https://coveralls.io/github/xJkit/react-goodbye?branch=master)
+[![NPM](https://img.shields.io/npm/v/react-goodbye.svg)](https://www.npmjs.com/package/react-goodbye) [![CircleCI](https://circleci.com/gh/xJkit/react-goodbye/tree/master.svg?style=shield)](https://circleci.com/gh/xJkit/react-goodbye/tree/master) [![Coverage Status](https://coveralls.io/repos/github/xJkit/react-goodbye/badge.svg?branch=master)](https://coveralls.io/github/xJkit/react-goodbye?branch=master) [![License: MIT](https://img.shields.io/badge/License-MIT-blue.svg)](https://github.com/xJkit/react-goodbye/blob/master/LICENSE)
 
 react-goodbye is a save reminder utility to prevent routing transition before you leave without saving changes.