Set textarea value when changing content

At http://jsfiddle.net/spicyj/W4QLq/, typing into the textbox would cause
clicking the button to do nothing; now it should work.
Don't set value if it'll be a noop
Don't let textarea value change via textContent

Turns out my tests before weren't particularly useful because
receiveProps doesn't end up running componentDidUpdate since the
transaction never finishes. Now they use replaceProps instead (and I
verified that commenting out the "rootNode.value = ..." line makes the
tests fail, which wasn't true before).
Adds optional callback to `setState`

This commit adds an optional callback as a second argument to
`setState`, to be called after `setState` runs.

We never guarantee synchronous execution of `setState`, and as per
@phunt, we don't want to make that guarantee because we may eventually
batch calls to `setState`.  @jwalke agrees with him.
Updated docs and check for truthiness

Change api docs to reflect presence of the new argument.  In addition,
callback was change to require only a "truthy" value.
markdown syntax

Small problem with markdown syntax in syntax-highlighted block.
Add callbacks to all public-facing state/props methods

All public facing {set,replace,force}{props,state} methods now support
callbacks.
Merge remote-tracking branch 'origin/master' into textarea-update-value
Don't update value or textContent unnecessarily

_updateDOMChildren was already updating textContent so we don't need to
do it in _updateDOMProperties. Additionally, don't update .value if
it'll be a noop because it has side-effects (like moving the cursor) in
some browsers (like IE 9).

Refactor tests to be a bit more robust and a bit cleaner too.
Remove textContent tests; they break in phantomjs
The compare_size cache gets wiped out with `grunt clean`

`.grunt/` is the directory that is suggested for storing task related
files, and this file is not useful if it gets wiped out often. So I'm
moving the compare_size cache into `.grunt/` so we keep it around
longer.
Check that `container` is a valid DOM element
Remove ReactID.primeTree in favor of priming in ReactID.getID.

Although it would have been nice to prime the entire tree and achieve a
cache hit rate of 100%, that cost would have to be paid up front, during
page rendering.

This patch avoids priming up front in favor of making the most of the work
done by `ReactMount.findReactRenderedDOMNodeSlow`, which calls
`ReactID.getID` while traversing the rendered DOM. The insight is this: if
`getID` simply primes the cache whenever it finds a new ID, then
`findReactRenderedDOMNodeSlow` will end up priming quite a few more nodes
that are actually involved in `ReactID.getNode` lookups, and we won't need
`primeTree` at all.
Remove ReactDOMNodeCache and getDOMNodeID.

These modules have been superseded by `ReactID`. Since they were only used
internally, and I have updated all client code that previously assumed
their existence, I believe they can be dropped for good.
Upgrade TextChangeEventPlugin to ChangeEventPlugin and support more form elements

Upgrade `TextChangeEventPlugin` to be the `onChange` event that React
fires. In React, `onChange` will now fire when `input` fires for form elements in
modern browsers.

Handle this for:

  input[type=text]
  input[type=password]
  input[type=checkbox]
  input[type=radio]
  textarea
  select

Support:

- OSX Chrome
- OSX Safari
- OSX Firefox
- Win 7 / IE8
- Win 7 / IE9
- Win 7 / IE10

Everything works but caret selection / placement differs from browser to
browser.

For <select> elements, the event is fired with `change`. This is a
conscious decision, even though in some browsers (OSX firefox, IE), it
can be argued that the event should fire more due to how the UI looks.

Builds on https://github.com/facebook/react/pull/75, which handled only
text inputs.
Enforce nodeCache validity

A node is considered valid if it

  1. has the expected ID (more of a sanity check than something that is
     ever likely to go wrong), and

  2. is contained by a currently mounted container.

When these requirements are met, we can be confident that
`ReactMount.findReactRenderedDOMNodeSlow(node.id) === node`, which is
important for cache consistency because `findReactRenderedDOMNodeSlow` is
what we fall back to when we don't find a node in the cache.

Point 2 is a subtle requirement, because it allows nodes to be valid even
if they are not currently contained by a document. Rendering into a
detached node is okay, in other words (which is something that
`document.getElementById` never properly accounted for).

Containment testing takes linear time in the depth of the DOM, which
sounds unfortunate until you realize that virtually all browsers support a
native `ancestor.contains(descendant)` method, and in practice the vast
majority of nodes are either orphaned with `.parentNode === null` or not
very deep relative to their container.
Make `@typechecks` static-only
Remove deleted files again

These accidentally got re-added in a rebase
Merge pull request #112 from spicyj/check-dom-nodetype

Check that `container` is a valid DOM element
Cache Default Props

The `getDefaultProps` return value should not be dependent on any external data (including `this.props` and `this.state`), so the return value should be consistent everytime we call it.

This caches the return value so we do not do work and allocate memory unnecessarily.