Sketch xray style generation as separate constructor.
Setup for tests.
Use testsource in vector tests.
Include fonts dir.
Add assertion for an xray style tile.
Add test for loading from source instance.
Add layername colorizer function.
Add xray support for interactivity/templates and test xray templating + colors.
Interactivity requires interactivity_fields param.
Use highlighted styling for active interactive layer.
Document additional constructors.
Merge pull request #51 from mapbox/xray-constructor

xray styles