let's scroll: part deux

`overflow-y: scroll auto` is a completely wrong way to write `overflow-y: auto`

[mdn overflow docs](https://developer.mozilla.org/en-US/docs/Web/CSS/overflow)

(i guess i've use it for so long because it works: facepalm)
Merge pull request #28 from diffalot/hide_overflow_scrollbar_when_inactive

let's scroll: part deux