use same one-entry-queue strategy from Scene.rebuildGeoemtry() for scene definition updates, Scene.updateStyles()
rename/consolidate some scene config methods
fix cases where child render modes were overwriting properties of parent modes
fix leaflet and worker tests
remove too-clever relative pathing, all config URLs are now just relative to root document
Merge branch 'master' into mode_refresh_queue
Merge pull request #48 from tangrams/mode_refresh_queue

Use throttle-with-single-entry-queue strategy for re-parsing styles & re-compiling GL programs
tests: add a custom shader to the scene fixture
Tile class work
Test some interactions between the Scene object and the Tile object
Pass the TileSource to the Tile object
Move over zoom calculation to tile source
Issue with Object.assign overriding values on Tile Object
Remove method
Fix tests
Fix broken leaftlet tests, move TileSource construction to create method