**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`
expect(e.getAttribute('width')).toBe('30');
      });
      itRenders('simple strings', async render => {
        const e = await render(<div width={'30'} />);
        expect(e.getAttribute('width')).toBe('30');
      });
      itRenders('no string prop with true value', async render => {
        const e = await render(<a href={true} />, 1);
        expect(e.hasAttribute('href')).toBe(false);
      });
      itRenders('no string prop with false value', async render => {
        const e = await render(<a href={false} />, 1);
        expect(e.hasAttribute('href')).toBe(false);
      });
      itRenders('no string prop with null value', async render => {
        const e = await render(<div width={null} />);
        expect(e.hasAttribute('width')).toBe(false);
      });
    });
    describe('boolean properties', function() {
      itRenders('boolean prop with true value', async render => {
        const e = await render(<div hidden={true} />);
        expect(e.getAttribute('hidden')).toBe('');
      });
      itRenders('boolean prop with false value', async render => {
        const e = await render(<div hidden={false} />);
        expect(e.getAttribute('hidden')).toBe(null);
      });
      itRenders('boolean prop with self value', async render => {
        const e = await render(<div hidden="hidden" />);