fix(doc): edit README

README.md

@@ -186,7 +186,7 @@ ReactDOM.render(
  <span>hello</span>
  <span>world</span>
  </NotesList>,
- document.body
+ document.getElementById('example')
 );
 ```
 
@@ -225,7 +225,7 @@ var data = 123;
 
 ReactDOM.render(
  <MyTitle title={data} />,
- document.body
+ document.getElementById('example')
 );
 ```
 
@@ -254,7 +254,7 @@ var MyTitle = React.createClass({
 
 ReactDOM.render(
  <MyTitle />,
- document.body
+ document.getElementById('example')
 );
 ```
 
@@ -346,7 +346,7 @@ var Input = React.createClass({
  }
 });
 
-ReactDOM.render(<Input/>, document.body);
+ReactDOM.render(<Input/>, document.getElementById('example'));
 ```
 
 More information on [official document](http:https://facebook.github.io/react/docs/forms.html).
@@ -389,7 +389,7 @@ var Hello = React.createClass({
 
 ReactDOM.render(
  <Hello name="world"/>,
- document.body
+ document.getElementById('example')
 );
 ```
 
@@ -442,7 +442,7 @@ var UserGist = React.createClass({
 
 ReactDOM.render(
  <UserGist source="https://api.github.com/users/octocat/gists" />,
- document.body
+ document.getElementById('example')
 );
 ```
 
@@ -459,7 +459,7 @@ ReactDOM.render(
  <RepoList
  promise={$.getJSON('https://api.github.com/search/repositories?q=javascript&sort=stars')}
  />,
- document.body
+ document.getElementById('example')
 );
 ```