Fix 'Unexpected strict mode reserved word', bump version to 1.3

Summary:
Looks like using 'let' was too ambitious :)

This should fix the issue https://github.com/facebook/react-native/issues/10976.

**Test plan (required)**

Travis & Circle CI tests on this PR.
Closes https://github.com/facebook/react-native/pull/11166

Differential Revision: D4237047

Pulled By: bestander

fbshipit-source-id: 85b548d74a0847621519364201cf71d6649ad605

react-native-cli/index.js

@@ -78,7 +78,7 @@ var REACT_NATIVE_PACKAGE_JSON_PATH = function() {
 // Use Yarn if available, it's much faster than the npm client.
 // Return the version of yarn installed on the system, null if yarn is not available.
 function getYarnVersionIfAvailable() {
-  let yarnVersion;
+  var yarnVersion;
   try {
     // execSync returns a Buffer -> convert to string
     if (process.platform.startsWith('win')) {
@@ -267,7 +267,7 @@ function getInstallPackage(rnPackage) {
 
 function run(root, projectName, rnPackage, forceNpmClient) {
   const yarnVersion = (!forceNpmClient) && getYarnVersionIfAvailable();
-  let installCommand;
+  var installCommand;
   if (yarnVersion) {
     console.log('Using yarn v' + yarnVersion);
     console.log('Installing ' + getInstallPackage(rnPackage) + '...');

react-native-cli/package.json

@@ -1,6 +1,6 @@
 {
   "name": "react-native-cli",
-  "version": "1.2.0",
+  "version": "1.3.0",
   "license": "BSD-3-Clause",
   "description": "The React Native CLI tools",
   "main": "index.js",