So this is a little self serving, but I think we should consider dropping support for IE9.  The data is interesting.  I'm seeing a [0.6% browser market share for IE9](https://netmarketshare.com/browser-market-share.aspx?options=%7B%22filter%22%3A%7B%22%24and%22%3A%5B%7B%22deviceType%22%3A%7B%22%24in%22%3A%5B%22Desktop%2Flaptop%22%5D%7D%7D%5D%7D%2C%22dateLabel%22%3A%22Trend%22%2C%22attributes%22%3A%22share%22%2C%22group%22%3A%22browserVersion%22%2C%22sort%22%3A%7B%22share%22%3A-1%7D%2C%22id%22%3A%22browsersDesktopVersions%22%2C%22dateInterval%22%3A%22Monthly%22%2C%22dateStart%22%3A%222017-07%22%2C%22dateEnd%22%3A%222018-06%22%2C%22segments%22%3A%22-1000%22%2C%22pageLength%22%3A50%7D).

What's neat about that data is that IE8 has twice the usage of IE9 🤷‍♂️ And IE10 has only 0.54% market share!  I could make a reasonable argument for dropping both IE9 *and* IE10.  

Of course, I'm only looking at this because I'd very much like to ship a new npm module with a few recently merged changes, and the IE9 tests are failing :)  

What are folks thoughts?  Does anyone feel strongly about the IE support matrix as it stands today?

@nickuraltsev @mzabriskie 
test/specs/utils/isX.spec.js
it('should validate Number', function () {
    expect(utils.isNumber(123)).toEqual(true);
    expect(utils.isNumber('123')).toEqual(false);
  });
  it('should validate Undefined', function () {
    expect(utils.isUndefined()).toEqual(true);
    expect(utils.isUndefined(null)).toEqual(false);
  });
  it('should validate Object', function () {
    expect(utils.isObject({})).toEqual(true);
    expect(utils.isObject(null)).toEqual(false);
  });
  it('should validate Date', function () {
    expect(utils.isDate(new Date())).toEqual(true);
    expect(utils.isDate(Date.now())).toEqual(false);
  });
  it('should validate Function', function () {
    expect(utils.isFunction(function () {})).toEqual(true);
    expect(utils.isFunction('function')).toEqual(false);
  });
  it('should validate Stream', function () {
    expect(utils.isStream(new Stream.Readable())).toEqual(true);
    expect(utils.isStream({ foo: 'bar' })).toEqual(false);
  });
  it('should validate URLSearchParams', function () {
    expect(utils.isURLSearchParams(new URLSearchParams())).toEqual(true);
    expect(utils.isURLSearchParams('foo=1&bar=2')).toEqual(false);
  });
});