**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`
expectTextNode(e.childNodes[1], 'b');
          expect(e.childNodes[2].childNodes.length).toBe(2);
          expectTextNode(e.childNodes[2].childNodes[0], 'c');
          expectTextNode(e.childNodes[2].childNodes[1], 'd');
          expectTextNode(e.childNodes[3], 'e');
        }
      });
    });
    describe('number children', function() {
      itRenders('a number as single child', async render => {
        const e = await render(<div>{3}</div>);
        expect(e.textContent).toBe('3');
      });
      
      itRenders('zero as single child', async render => {
        const e = await render(<div>{0}</div>);
        expect(e.textContent).toBe('0');
      });
      itRenders('an element with number and text children', async render => {
        const e = await render(<div>{'foo'}{40}</div>);
        
        if (
          render === serverRender ||
          render === clientRenderOnServerString ||
          render === streamRender
        ) {
          
          expect(e.childNodes.length).toBe(3);
          expectTextNode(e.childNodes[0], 'foo');
          expectTextNode(e.childNodes[2], '40');