clearfix: Refactoring needed

[tadatuta]

Right now we have clearfix.ie.css but we do not build ie.css bundle. So we have 2 options:

1. Move ie.css source to common css
2. As we do not support IE6-7 it's possible to refactor clearfix to

.clearfix:after {
    content: "";
    display: table;
    clear: both;
}

[tadatuta]

// cc @mishanga

[mishanga]

I like second one.
But why table?

[tadatuta]

Here's an explanation: http://nicolasgallagher.com/micro-clearfix-hack/

[aristov]

Assign an issue to yourself, if you make PR for it, please.