Better layer sorting to fix z-depth issues..
Group line parts so that they can be properly depth sorted.
Group by layer to correctly depth sort lines..
Merge branch 'master' into bhousel-layers
Precreate fixed number of layergroups between -10, 10
improve bridge styles, add low-zoom, butt linecaps..
add test for iD.Entity.layer(), fix spelling of man_made.
separate svg group for areas and their related strokes/fills
(for consistency)
Add tests for line z-indexing.
Remove obsolete tests
Merge branch 'refs/heads/bhousel-bhousel-layers'