**Do you want to request a *feature* or report a *bug*?**
Bug

**What is the current behavior?**
I've started recieving this warning about my SVGs which is using [feGaussianBlur](https://developer.mozilla.org/en-US/docs/Web/SVG/Element/feGaussianBlur): 
`Warning: Expected server HTML to contain a matching <feGaussianBlur> in <filter>.`

**What is the expected behavior?**
Should be no warnings because there are no difference.

**Which versions of React, and which browser / OS are affected by this issue? Did this work in previous versions of React?**
Such behavior started right after updating to `React 16.0.0-rc.3` and never happened with `React 15.6.1`
newText: string,
  ): void {
    textInstance.nodeValue = newText;
  },
  appendChild(parentInstance: Instance, child: Instance | TextInstance): void {
    parentInstance.appendChild(child);
  },
  appendChildToContainer(
    container: Container,
    child: Instance | TextInstance,
  ): void {
    if (container.nodeType === COMMENT_NODE) {
      (container.parentNode: any).insertBefore(child, container);
    } else {
      container.appendChild(child);
    }
  },
  insertBefore(
    parentInstance: Instance,
    child: Instance | TextInstance,
    beforeChild: Instance | TextInstance,
  ): void {
    parentInstance.insertBefore(child, beforeChild);
  },
  insertInContainerBefore(
    container: Container,
    child: Instance | TextInstance,
    beforeChild: Instance | TextInstance,
  ): void {
    if (container.nodeType === COMMENT_NODE) {