Add top-level API docs section for React.createElement.
Adding link to wiki

Based on conversation in https://github.com/facebook/react/pull/2501. A good place to guide people further in finding the complete set of tools needed to build an application.
add note re: handling events in capture phase
Fix addons documentation of development only part
Merge pull request #2633 from koba04/fix-addons-document

Fix addons documentation of development only part
Update ref-05-events.md

use backticks and change example into its own sentence
[docs] Clarify when state may duplicate props
[docs] Remove generic spread, Object.assign  mentions
Merge pull request #2616 from christianalfoni/patch-3

Adding link to wiki
Own our fiddles so we can update them more easily
Screencast interfacing react + backbone
Merge pull request #2623 from jbhatab/patch-1

Screencast interfacing react + backbone
Merge pull request #2622 from rafd/patch-1

add note re: handling events in capture phase
Merge pull request #2636 from zpao/docs/spread-assign-update

[docs] Remove generic spread, Object.assign  mentions
Merge pull request #2615 from af/createElement-docs

Add top-level API docs section for React.createElement.
Remove unused require from ReactDOM-test

This happened internally in a codemod
In `Transferring Props` guide, `Manual Transfer` section will lead an error

```c
var FancyCheckbox = React.createClass({
  render: function() {
    var fancyClass = this.props.checked ? 'FancyChecked' : 'FancyUnchecked';
    return (
      <div className={fancyClass} onClick={this.props.onClick}>
        {this.props.children}
      </div>
    );
  }
});
React.render(
  <FancyCheckbox checked={true} onClick={console.log}>
    Hello world!
  </FancyCheckbox>,
  document.body
);
```

When click `Hello world!` will lead a `Uncaught TypeError: Illegal invocation` error
Use String.charAt for character by index lookup

Using object property accessor for string character lookup breaks in
non-modern browsers.
Merge pull request #2651 from arnihermann/use-charat-not-string-index-markup-diff

Use String.charAt to lookup string characters by index
Merge pull request #2649 from cookfront/master

In `Transferring Props` guide, `Manual Transfer` section will lead an er...