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These modules have been superseded by `ReactID`.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