Tweak goBack docs a bit

docs/guides/NavigatingOutsideOfComponents.md

@@ -3,15 +3,23 @@
 While you can use `this.props.router` from `withRouter` to navigate around, many apps want to be able to navigate outside of their components. They can do that with the history the app gives to `Router`.
 
 ```jsx
-// your main file that renders a Router
+// Your main file that renders a <Router>:
 import { Router, browserHistory } from 'react-router'
 import routes from './app/routes'
-render(<Router history={browserHistory} routes={routes}/>, el)
+
+render(
+  <Router history={browserHistory} routes={routes} />,
+  mountNode
+)
 ```
 
 ```jsx
-// somewhere like a redux/flux action file:
+// Somewhere like a Redux middleware or Flux action:
 import { browserHistory } from 'react-router'
-browserHistory.push('/some/path') // go to /some/path page
-browserHistory.goBack() // go back to previous page
+
+// Go to /some/path.
+browserHistory.push('/some/path')
+
+// Go back to previous location.
+browserHistory.goBack()
 ```