Exclude feature loader MVT test from IE9

[bartvde]

closes #4560

[ahocevar]

Instead of

describe('foo', function() {
  beforeEach(function() {
    // setup
  });
  it('bar', function() {
    // the only test in this describe block
  })
});

it would be nicer to do

it('foo bar', function() {
  // setup
  // the only test in this describe block
});

Would make the tests easier to read, and you can do xit instead of xdescribe.

[bartvde]

agreed, will make the change

[ahocevar]

Looks good now. Please merge when Travis has finished their review.