add installation information

Author: ryanflorence

packages/react-router-website/modules/api/Installation.md

@@ -0,0 +1,74 @@
+# Installation {id=installation}
+
+React Router runs in multiple environments: browsers, servers, native, and even VR (works in the dev preview!) While many components are shared (like `Route`) others are specific to environment (like `NativeRouter`).  Rather than requiring you install two packages, you only have to install the package for the target environment. Any shared components between the environments are re-exported from the environment specific package.
+
+## Web {id=installationweb}
+
+```bash
+npm install react-router-dom@next`
+# or
+yarn add react-router-dom@next
+```
+
+All of the package modules can be imported from the top:
+
+```js
+import {
+  BrowserRouter as Router
+  StaticRouter // for server rendering
+  Route,
+  Link
+  // etc.
+} from 'reat-router-dom'
+```
+
+If you're going for a really minimal bundle sizes on the web you can import modules directly. Theoretically a tree-shaking bundler like Webpack makes this unnecessary but we haven't tested it yet. We welcome you to!
+
+```js
+import Router from 'react-router-dom/BrowserRouter'
+import Route from 'react-router/Router'
+// etc.
+```
+
+## Native {id=installation.native}
+
+We're still working on great documentation for the native capabilities of React Router. For now we recommend you [read the source](https://github.com/ReactTraining/react-router/tree/v4/packages/react-router-native).
+
+```bash
+yarn add react-router-native@next
+# or if not using the react-native cli
+npm install react-router-native@next
+```
+
+All of the package modules can be imported from the top:
+
+```js
+import {
+  NativeRouter as Router
+  DeepLinking,
+  AndroidBackButton,
+  Link,
+  Route
+  // etc.
+} from 'react-router-native'
+```
+
+## Who-knows-where {id=installation.who-knows-where}
+
+```bash
+yarn add react-router@next
+# or if not using the react-native cli
+npm install react-router@next
+```
+
+All of the package modules can be imported from the top:
+
+```js
+import {
+  MemoryRouter as Router,
+  Route
+  // etc.
+} from 'reat-router'
+```
+
+You can use React Router's navigation anywhere you run React, the navigation state is kept in a memory router. You can look at the implementation of NativeRouter to get an idea on how to integrate.

packages/react-router-website/modules/components/APIDocs.js

@@ -6,21 +6,24 @@ import MarkdownViewer from './MarkdownViewer'
 import ScrollToMe from './ScrollToMe'
 
 export const API = [
+  { name: 'Installation',
+    html: require('../api/Installation.md')
+  },
   { name: 'BrowserRouter',
     html: require('../api/BrowserRouter.md')
   },
-  { name: 'HashRouter',
-    html: require('../api/HashRouter.md')
-  },
-  { name: 'MemoryRouter',
-    html: require('../api/MemoryRouter.md')
-  },
   { name: 'NativeRouter',
     html: require('../api/NativeRouter.md')
   },
   { name: 'StaticRouter',
     html: require('../api/StaticRouter.md')
   },
+  { name: 'HashRouter',
+    html: require('../api/HashRouter.md')
+  },
+  { name: 'MemoryRouter',
+    html: require('../api/MemoryRouter.md')
+  },
   { name: 'Router',
     html: require('../api/Router.md')
   },