fix(rest): Add index boilerplate

Author: kjdelisle

packages/rest/index.d.ts

@@ -0,0 +1,6 @@
+// Copyright IBM Corp. 2017. All Rights Reserved.
+// Node module: @loopback/rest
+// This file is licensed under the MIT License.
+// License text available at https://opensource.org/licenses/MIT
+
+export * from './lib';

packages/rest/index.js

@@ -0,0 +1,9 @@
+// Copyright IBM Corp. 2017. All Rights Reserved.
+// Node module: @loopback/rest
+// This file is licensed under the MIT License.
+// License text available at https://opensource.org/licenses/MIT
+
+const nodeMajorVersion = +process.versions.node.split('.')[0];
+module.exports = nodeMajorVersion >= 7 ?
+  require('./lib') :
+  require('./lib6');