Remove isStatic

This can be replicated with a custom component that always returns false`
from `shouldComponentUpdate`. A generic implementation might look like:

```
var StaticContainer = React.createClass({
  shouldComponentUpdate: function() {
    return false;
  },

  render: function() {
    return this.transferPropsTo(this.props.children[0]);
  }
});
```

And then used in JSX as
`<StaticContainer><div>Hello!</div></StaticContainer>`, resulting in
only `<div>Hello!</div>` being inserted into the DOM.

src/core/ReactCompositeComponent.js

@@ -679,9 +679,7 @@ var ReactCompositeComponentMixin = {
     var currentComponent = this._renderedComponent;
     var nextComponent = this._renderValidatedComponent();
     if (currentComponent.constructor === nextComponent.constructor) {
-      if (!nextComponent.props.isStatic) {
-        currentComponent.receiveProps(nextComponent.props, transaction);
-      }
+      currentComponent.receiveProps(nextComponent.props, transaction);
     } else {
       // These two IDs are actually the same! But nothing should rely on that.
       var thisID = this._rootNodeID;

src/core/ReactMultiChild.js

@@ -167,8 +167,7 @@ var ReactMultiChildMixin = {
           this.enqueueMove(curChild._domIndex, loopDomIndex);
         }
         curChildrenDOMIndex = Math.max(curChild._domIndex, curChildrenDOMIndex);
-        !nextChild.props.isStatic &&
-          curChild.receiveProps(nextChild.props, transaction);
+        curChild.receiveProps(nextChild.props, transaction);
         curChild._domIndex = loopDomIndex;
       } else {
         if (curChild) {               // !shouldUpdate && curChild => delete