"checkbox" not "checked"

I can only assume this was a typo.
Add dataType to all $.ajax calls for consistency

Fixes https://groups.google.com/forum/#!topic/reactjs/WWA3ZqU6y4w.
Allow null return values for functions to-be-merged.
Update docs to mention that you need both es5-shim.js and es5-sham.js to use React with IE8.
Fix typo in docs.
Make findComponentRoot faster with more nodeCache

This is an alternative, less-invasive, fix for #891.

Test Plan:
On http://jsbin.com/OqOJidIQ/2/edit, got timings like

[75, 56, 30, 36, 27, 27, 28, 32, 27, 27, 28, 31]

instead of the old

[75, 729, 46, 32, 28, 34, 26, 27, 27, 30, 26, 26].

I also added a counter to getID and saw it was called 3014 times instead of the old 636264. (3014 is the number of nodes (3000) plus 3 calls that happen for the initial render and 1 for each of the 11 renders after that.)
Merge pull request #884 from spicyj/tut-datatype

Add dataType to all $.ajax calls for consistency
Merge pull request #895 from spicyj/zomgperf

Make findComponentRoot faster with more nodeCache
Wrap _performComponentUpdate call in try/finally

Fixes #208. If you attempt a state update with a bad state then the render will fail (and the DOM won't change) but if you switch back to a valid state later then it'll rerender properly.
Fix "Uncontrolled Components" documentation
Rewrite Older Browsers polyfill section for clarity.
Merge pull request #892 from rtfeldman/update-shim-docs

Mention need for `es5-sham.js` in docs
Merge pull request #897 from spicyj/gh-208

Wrap _performComponentUpdate call in try/finally
Merge pull request #881 from spicyj/checkbox-not-checked

"checkbox" not "checked"
Remove stray "117", combine lines in polyfill docs
[docs] Add timezone to _config

This way we hopefully won't churn the feed when genereated in
a different time zone (eg France).
[docs] Remove commented out ghbtns
throw when using component/component class as mixin

throw invariant error to help people new to mixins, so that they don't get misled into trying to mixin components into another component
Introduce PropTypes.shape

This diff introduces PropType.shape which lets you type an object. PropType.object was already defined and since it isn't a function I couldn't really overload the meaning to also accept a type list. Instead of doing hackery, I decided to name it `shape`.

An example where this could be used is style:

```
  propTypes: {
    style: PropTypes.shape({
      color: PropStyle.string,
      fontSize: PropTypes.number
    })
  }
```
Add `topContextMenu` to the event dependencies for `SelectEventPlugin`