Maps: use labels instead of tooltips

A fellow in Leaflet's gitter [showed me](https://gitter.im/Leaflet/Leaflet?at=59c8f071bc464729747258bd) how he's used `L.tooltip` for labels:


Tooltip options:
```js
{permanent: true}
```

And styles:
```css
.leaflet-tooltip {
background: none;
box-shadow: none;
border: none;
}
.leaflet-tooltip-left:before, .leaflet-tooltip-right:before {
border: 0px;
}
```

And to prevent overlapping labels, we can use [Geovation/labelgun](https://github.com/Geovation/labelgun). Woot!