**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`
jest.resetModuleRegistry();
  
  ExecutionEnvironment = require('ExecutionEnvironment');
  PropTypes = require('prop-types');
  React = require('react');
  ReactDOM = require('react-dom');
  ReactTestUtils = require('react-dom/test-utils');
  
  
  
  jest.resetModuleRegistry();
  ReactDOMServer = require('react-dom/server');
}
describe('ReactDOMServerIntegration', () => {
  beforeEach(() => {
    resetModules();
    ExecutionEnvironment.canUseDOM = false;
  });
  describe('basic rendering', function() {
    itRenders('a blank div', async render => {
      const e = await render(<div />);
      expect(e.tagName).toBe('DIV');
    });
    itRenders('a self-closing tag', async render => {
      const e = await render(<br />);
      expect(e.tagName).toBe('BR');
    });
    itRenders('a self-closing tag as a child', async render => {