The sidebar arrows should change content when they're open. There's a small bug in css/customstyles.css that prevents this; other parts of the style use 'active' instead of 'open' so it needs to here too.
This PR fixes it.
Since Font Awesome is already wired in, I think that their carets look nicer. Here's how:
```
.nav li > a > span:after {
font-family: FontAwesome;
content: "\f105";
}
.nav li.active > a > span:after {
font-family: FontAwesome;
content: "\f107";
}
```
dfe9602384