Scroll helpers

<div class="mod">
<div class="scroll-if-needed">
Applies overflow: auto to element.
If you need only horizontal scroll, use scroll-horizontal-if-needed.
<div class="mod--hidden">
<div class="no-scroll">
Applies overflow: hidden to element.
<div class="scroll-smooth-touch">
Applies -webkit-overflow-scrolling: touch to element (scroll with a kind of inertia on iOS Safari). (careful, this creates a stacking context)