**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`
itRenders('simple strings', async render => {
        const e = await render(<div aria-label="hello" />);
        expect(e.getAttribute('aria-label')).toBe('hello');
      });
      
      itRenders('aria string prop with false value', async render => {
        const e = await render(<div aria-label={false} />);
        expect(e.getAttribute('aria-label')).toBe('false');
      });
      itRenders('no aria prop with null value', async render => {
        const e = await render(<div aria-label={null} />);
        expect(e.hasAttribute('aria-label')).toBe(false);
      });
      itRenders('"aria" attribute with a warning', async render => {
        
        const e = await render(<div aria="hello" />, 1);
        expect(e.getAttribute('aria')).toBe('hello');
      });
    });
    describe('cased attributes', function() {
      itRenders(
        'badly cased aliased HTML attribute with a warning',
        async render => {
          const e = await render(<meta httpequiv="refresh" />, 1);
          expect(e.hasAttribute('http-equiv')).toBe(false);
          expect(e.getAttribute('httpequiv')).toBe('refresh');
        },
      );
      itRenders('badly cased SVG attribute with a warning', async render => {
        const e = await render(<text textlength="10" />, 1);