docs($q): describe your change...

IMO while IE8 support is dropped from 1.3.x, there are still a lot of people using 1.2 for the purposes of supporting IE8. For this reason, I think it would be nice to mention the potential problem when using ".catch" in IE8 and a quick reference to the correct way of referencing it (either using ['catch'] or just using the 2nd callback in .then()). If this is not the appropriate location however, maybe a better place for this would be the section titled [Internet Explorer Compatibility](https://docs.angularjs.org/guide/ie)