remove extra <br>s around images

[meetar]

Seeing some extra space between code blocks and images in a docs page (https://precog.mapzen.com/mapzen/documentation/meetar/unembed-tutorial2/documentation/tangram/custom-styles/):

Markdown code looks like this:

```yaml
sources:
    mapzen:
        type: TopoJSON
        url: https://tile.mapzen.com/mapzen/vector/v1/all/{z}/{x}/{y}.topojson

layers:
    roads:
        data: { source: mapzen }
        draw:
            lines:
                order: 1
                width: 5px
                color: gray
```
![simple road map](https://tangrams.github.io/tangram-docs/tutorials/custom/custom1.jpg)

And resulting html looks like this in the dev pane:

I'm seeing <br> tags on either side of the <img> – would it be possible to remove those from the build process?