Attempt to get window resizing working
Resolving warnings in TileLayer.
Resolving warnings in the layer library.
Resolving warnings in the handler library.
Merge branch 'resizing' of https://github.com/justinfagnani/leaflet.dart into justinfagnani-resizing

Conflicts:
	lib/layer/layer.dart
	lib/layer/marker/marker.dart
	lib/layer/tile/tile_layer.dart
	lib/map/handler/drag.dart
	lib/map/map.dart
Merge branch 'justinfagnani-resizing'
Combining map options.