convert compare script to python so we don't need node in -native
Merge pull request #9 from mapbox/python

Convert compare script to Python so we don't need node in -native
Start v6
v6 line-offset -> line-gap-width
Render ⇢ layout, style ⇢ paint

https://github.com/mapbox/mapbox-gl-style-spec/issues/166
Add text-keep-upright tests