The complete move to MIT license (#115)

- headers in .js files
- update README and LICENSE year

Testing:

grep BSD, Patents, patents turned up nothing

lib/core/Site.js

@@ -1,10 +1,8 @@
 /**
  * Copyright (c) 2017-present, Facebook, Inc.
- * All rights reserved.
  *
- * This source code is licensed under the BSD-style license found in the
- * LICENSE file in the root directory of this source tree. An additional grant
- * of patent rights can be found in the PATENTS file in the same directory.
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
  */
 
 const React = require("react");
@@ -75,7 +73,7 @@ class Site extends React.Component {
             `
               }}
             />}
-          {this.props.config.facebookAppId && 
+          {this.props.config.facebookAppId &&
             <script
               dangerouslySetInnerHTML={{
                 __html: `window.fbAsyncInit = function() {FB.init({appId:'${this.props.config.facebookAppId}',xfbml:true,version:'v2.7'});};(function(d, s, id){var js, fjs = d.getElementsByTagName(s)[0];if (d.getElementById(id)) {return;}js = d.createElement(s); js.id = id;js.src = '//connect.facebook.net/en_US/sdk.js';fjs.parentNode.insertBefore(js, fjs);}(document, 'script','facebook-jssdk'));
@@ -83,7 +81,7 @@ class Site extends React.Component {
               }}
             />
           }
-          {this.props.config.twitter && 
+          {this.props.config.twitter &&
             <script
               dangerouslySetInnerHTML={{
                 __html: `window.twttr=(function(d,s, id){var js,fjs=d.getElementsByTagName(s)[0],t=window.twttr||{};if(d.getElementById(id))return t;js=d.createElement(s);js.id=id;js.src='https://platform.twitter.com/widgets.js';fjs.parentNode.insertBefore(js, fjs);t._e = [];t.ready = function(f) {t._e.push(f);};return t;}(document, 'script', 'twitter-wjs'));`,