CHANGELOG updated

Layers Singleton added
Merge branch 'master' of https://github.com/kekscom/osmbuildings

Conflicts:
	dist/L.BuildingsLayer-debug.js
	dist/L.BuildingsLayer.js
	dist/OpenLayers.Layer.Buildings-debug.js
	dist/OpenLayers.Layer.Buildings.js
	src/FlatBuildings.js
	src/Layers.js
	src/Shadows.js
	src/events.js
	src/properties.js
	src/public.js
	src/render.js