Hover not working on IE 11

@markmarkoh I'm sorry to say that the bug #19 is happening again. This time is happening because of the "isIE" test.

```javascript
if ( ! /MSIE/.test(navigator.userAgent) ) {
    moveToFront.call(this);
}
```

After IE11 update the userAgent has no longer the word MSIE, so it's not safe anymore to check if it's IE with this regex test. I added another test with the token "Trident". Although it's working for now, a new release of IE might broke this again.

Why it's necessary to use that "moveToFront" method?