Add ol.tilegrid.TileGrid.getTileCoordChildTileRange
Use high resolution tiles in WebGL renderer
Use high resolution tiles in Canvas renderer
Use high resolution tiles in DOM renderer
Store maxZoom in ol.tilegrid.XYZ
Add optimized version of getTileCoordChildTileRange for ol.tilegrid.XYZ
Remove preload from examples that don't need it
Propagate return value
Merge pull request #509 from twpayne/use-high-resolution-tiles

Use high resolution tiles