Hello, React Native

这个东西最近比较火，我也忍不住拿来研究一番

1. 安装Node
   brew install node
   设置镜像
   npm config set registry https://registry.npm.taobao.org --global
   npm config set disturl https://npm.taobao.org/dist --global
2. 安装Yarn, Facebook提供的替代npm的工具，可以加速node模块的下载
   brew install yarn
   设置镜像
   yarn config set registry https://registry.npm.taobao.org --global
   yarn config set disturl https://npm.taobao.org/dist --global
   注意不建议使用npm安装yarn,参见https://yarnpkg.com/lang/en/docs/install/#alternatives-tab
   Note: Installation via npm is generally not recommended. npm is non-deterministic, packages are not signed, and npm does not perform any integrity checks other than a basic SHA1 hash, which is a security risk when installing system-wide apps.
   For these reasons, it is highly recommended that you install Yarn through the installation method best suited to your operating system.
3. 安装React Native的命令行工具（react-native-cli）
   npm install -g react-native-cli
   4.安装Xcode或者Android Studio
4. 安装Watchman以及官方推荐的Atom插件Nuclide
   brew install watchman
   Nuclide只能在Atom中起一个server,运行应用还得回到命令行react-native run-xxx

预备工作完成，可以开始创建一个项目了：
react-native init HelloWorld
cd HelloWorld
react-native run-ios 或者 react-native run-android
注意项目创建后名字不能随便改，否则会出错，另外项目不要起名太高端，比如叫ReactNative，这种名字会给自己找麻烦，对，我就找了一回。
还要注意运行安卓之间必须保证有模拟器已经在运行中。