One way arrows are not reversed correctly when oneway=-1

Hi,

just had the problem, that the arrows on a oneway street where heading in the wrong direction. Turned out that it is a oneway=-1 street. The Carto code in OSM Bright is

```
[oneway=-1] { marker-file: url(img/icon/oneway-reverse.svg); }
```

But the oneway-value is not stored as integer in my osm2pgsql import, so I fixed this using:

```
[oneway='-1'] { marker-file: url(img/icon/oneway-reverse.svg); }
```

Thanks for the beautiful start-off-theme!
Tom

Search the OSM Bright CartoCSS rules for the shown [oneway=-1] marker-file condition. Change the comparison to match the string value produced by the osm2pgsql import, then verify that oneway=-1 streets use the reverse arrow marker.

Written by the indexing model from the issue text.