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/write-translations.js

@@ -2,11 +2,9 @@
 
 /**
  * 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.
  */
 
 /* generate the i18n/en.json file */
@@ -63,7 +61,7 @@ function execute() {
     }
   });
 
-  // find sidebar category titles to translate 
+  // find sidebar category titles to translate
   Object.keys(sidebars).forEach(sb => {
     const categories = sidebars[sb];
     Object.keys(categories).forEach(category => {