Initial version of the global cli

Test Plan:

```
npm pack
node global-cli/index.js testing --scripts-version /Users/vjeux/random/react-getting-started/create-react-app-scripts-0.0.1.tgz
```

make sure it shows

```
Creating the app testing at /Users/vjeux/random/react-getting-started/testing
```

Author: vjeux

.gitignore

@@ -1,3 +1,4 @@
 node_modules/
 build
 .DS_Store
+*.tgz

global-cli/index.js

@@ -0,0 +1,159 @@
+#!/usr/bin/env node
+
+/**
+ * Copyright (c) 2015-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.
+ */
+
+// ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+// /!\ DO NOT MODIFY THIS FILE /!\
+// ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+//
+// create-react-app is installed globally on people's computers. This means
+// that it is extremely difficult to have them upgrade the version and
+// because there's only one global version installed, it is very prone to
+// breaking changes.
+//
+// The only job of create-react-app is to init the repository and then
+// forward all the commands to the local version of create-react-app.
+//
+// If you need to add a new command, please add it to local-cli/.
+//
+// The only reason to modify this file is to add more warnings and
+// troubleshooting information for the `react init` command.
+//
+// Do not make breaking changes! We absolutely don't want to have to
+// tell people to update their global version of create-react-app.
+//
+// ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+// /!\ DO NOT MODIFY THIS FILE /!\
+// ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+'use strict';
+
+var fs = require('fs');
+var path = require('path');
+var exec = require('child_process').exec;
+var spawn = require('child_process').spawn;
+var chalk = require('chalk');
+var semver = require('semver');
+/**
+ * Used arguments:
+ *   -v --version - to print current version of create-react-app and create-react-app-scripts dependency
+ *   --verbose - to print logs while init
+ *   --scripts-version <alternative create-react-app-scripts package> - override default (https://registry.npmjs.org/create-react-app-scripts@latest),
+ *      package to install, examples:
+ *     - "0.22.0-rc1" - A new app will be created using a specific version of React CLI from npm repo
+ *     - "https://registry.npmjs.org/create-react-app-scripts/-/create-react-app-scripts-0.20.0.tgz" - a .tgz archive from any npm repo
+ *     - "/Users/home/create-react-app/create-react-app-scripts-0.22.0.tgz" - for package prepared with `npm pack`, useful for e2e tests
+ */
+var argv = require('minimist')(process.argv.slice(2));
+
+var commands = argv._;
+if (commands.length === 0) {
+  console.error(
+    'Usage: create-react-app <project-name> [--verbose]'
+  );
+  process.exit(1);
+}
+
+if (argv.v || argv.version) {
+  console.log('create-react-app: ' + require('./package.json').version);
+  process.exit();
+}
+
+createApp(commands[0], argv.verbose, argv['scripts-version']);
+
+function createApp(name, verbose, version) {
+  if (fs.existsSync(name)) {
+    console.log('Directory `' + name + '` already exists. Aborting.');
+    process.exit();
+  }
+
+  var root = path.resolve(name);
+  var appName = path.basename(root);
+
+  console.log(
+    'This will walk you through creating a new React app in',
+    root
+  );
+
+  fs.mkdirSync(root);
+
+  var packageJson = {
+    name: appName,
+    version: '0.0.1',
+    private: true,
+  };
+  fs.writeFileSync(path.join(root, 'package.json'), JSON.stringify(packageJson));
+  process.chdir(root);
+
+  console.log('Installing create-react-app-scripts package from npm...');
+
+  run(root, appName, version, verbose);
+}
+
+function run(root, appName, version, verbose) {
+  var args = [
+    'install',
+    verbose && '--verbose',
+    '--save',
+    '--save-exact',
+    getInstallPackage(version),
+  ].filter(function(e) { return e; });
+  var proc = spawn('npm', args, {stdio: 'inherit'});
+  proc.on('close', function (code) {
+    if (code !== 0) {
+      console.error('`npm ' + args.join(' ') + '` failed');
+      return;
+    }
+
+    var scriptsPath = path.resolve(
+      process.cwd(),
+      'node_modules',
+      'create-react-app-scripts',
+      'init.js'
+    );
+    var init = require(scriptsPath);
+    init(root, appName);
+  });
+}
+
+function getInstallPackage(version) {
+  var packageToInstall = 'create-react-app-scripts';
+  var validSemver = semver.valid(version);
+  if (validSemver) {
+    packageToInstall += '@' + validSemver;
+  } else if (version) {
+    // for tar.gz or alternative paths
+    packageToInstall = version;
+  }
+  return packageToInstall;
+}
+
+function checkNodeVersion() {
+  var packageJsonPath = path.resolve(
+    process.cwd(),
+    'node_modules',
+    'create-react-app-scripts',
+    'package.json'
+  );
+  var packageJson = require(packageJsonPath);
+  if (!packageJson.engines || !packageJson.engines.node) {
+    return;
+  }
+  if (!semver.satisfies(process.version, packageJson.engines.node)) {
+    console.error(
+      chalk.red(
+        'You are currently running Node %s but React CLI requires %s. ' +
+        'Please use a supported version of Node.\n'
+      ),
+      process.version,
+      packageJson.engines.node
+    );
+  }
+}

global-cli/package.json

@@ -0,0 +1,12 @@
+{
+  "name": "create-react-app",
+  "version": "1.0.0",
+  "bin": {
+    "create-react-app": "index.js"
+  },
+  "dependencies": {
+    "chalk": "^1.1.1",
+    "minimist": "^1.2.0",
+    "semver": "^5.0.3"
+  }
+}

init.js

@@ -0,0 +1,3 @@
+module.exports = function(root, appName) {
+  console.log('Creating the app', appName, 'at', root);
+};

package.json

@@ -1,5 +1,6 @@
 {
-  "name": "react-getting-started",
+  "name": "create-react-app-scripts",
+  "version": "0.0.1",
   "scripts": {
     "start": "cross-env NODE_ENV=development node devServer.js",
     "build": "rimraf build && cross-env NODE_ENV=production webpack --config webpack.config.prod.js"