Use React.autoBind by default.

Per our discussion - this is the general approach we'd like to take for
the public facing API.

    var MyComponent = React.createClass({
      render: function() {
        return <div onClick={this.myCallback} />;
      },
      myCallback: function() {
      }
    });
fix bad caching in ReactID.getID
Fix a bunch of problems with implicit autobinding
Clean up naming

Fix a small style nit
Add unit test to prevent regression

The original autobinding diff made some assumptions about how methods were called on components that had to be reverted. This diff
enforces those assumptions in a test
Dynamic Input Component

Summary:
This is a proposal based loosely on the discussions I've had with @paulshen and @jwalke. It implements a shim for `React.DOM.input` (used as `<input>`) that supports two different use cases depending on whether `value` is provided or not.

If a `value` is //not// provided, the input will be initialized with the empty string (or `defaultValue`) and anytime the user changes the input, the `onChange` (or `onTextChange`) handler will be fired and the DOM will reflect the new changes.

  React.renderComponent(
    <input type="text" defaultValue="Untitled" onTextChange={handleChange} />,
    container
  );

If a `value` is provided, the input will be initialized to that value. Anytime the user changes the input, the `onChange` (or `onTextChange`) handler will be fired. However, the DOM will //not// reflect the new changes. If a `value` is provided, it is the responsibility of the owner to update the `value` prop passed in.

  var value = "Untitled";
  var input = React.renderComponent(
    <input type="text" value={value} onTextChange={handleChange} />,
    container
  );
  function handleChange(event) {
    // Do something cool like strip out non-numbers.
    var value = event.target.value.replace(/\D/g, '');
    input.setProps({value: value});
  }

This is just a start and we should build similar components for `textarea` and `select`. Also, this does not inject the new components because the changes are not backward compatible. Once we change all `<input>` uses to use `ReactDOMInput`, then we can inject.
Fix isMounted() for composite components

This behavior seemed incorrect for composite components.

- isComponentMounted() represents ReactComponent's lifecycle of mounting
- isMounted() represents ReactCompositeComponent's lifecycle of isMounted()

Therefore, ReactComponents no longer have isMounted(). I think this is fine since it was not supposed to be public anyway.
Require Statement Nits
Use `@return`, not `@returns`