Render traffic calming tagged on ways

[samcantwell]

The OSM wiki describes tagging speed tables as ways as an acceptable form of tagging, and there are many example ways tagged as speed tables. Currently, Cyclosm only renders speed tables tagged on nodes. This should be extended to include those tagged on ways.

Perhaps this could be rendered as one half of the normal speed table icon for Cyclosm that is placed at the boundary between ways with the speed table tag and ways without.