It seems problematic to allow arbitary non-lowercase attribute on HTML nodes. Because the server has no ability to keep them case sensitive (HTML isn't). So they will end up different on the client.

We should probably warn if the attribute is not a known one *and* is not lowercase.
expect(stubStyle.display).toEqual('block');
      expect(stubStyle.left).toEqual('1px');
      expect(stubStyle.top).toEqual('2px');
      expect(stubStyle.fontFamily).toEqual('Arial');
      
      var reset = {display: '', left: null, top: false, fontFamily: true};
      ReactDOM.render(<div style={reset} />, container);
      expect(stubStyle.display).toEqual('');
      expect(stubStyle.left).toEqual('');
      expect(stubStyle.top).toEqual('');
      expect(stubStyle.fontFamily).toEqual('');
    });
    it('should not update styles when mutating a proxy style object', () => {
      var styleStore = {display: 'none', fontFamily: 'Arial', lineHeight: 1.2};
      
      
      var styles = {
        get display() {
          return styleStore.display;
        },
        set display(v) {
          styleStore.display = v;
        },
        get fontFamily() {
          return styleStore.fontFamily;
        },
        set fontFamily(v) {
          styleStore.fontFamily = v;
        },
        get lineHeight() {