Preserve line breaks when showing sweep description
Preserve line breaks when showing sweep description

On the `SweepsController#show` page, we display the sweep description.
Previously, the text would be displayed in a big blob, without line
breaks. By passing it through `simple_format`, we get a better output
(with line breaks).

kalw/diffux,kalw/diffux,diffux/diffux,diffux/diffux,diffux/diffux,kalw/diffux