Add support for maxNativeZoom

[mairsbw]

I don't see this anywhere in the codebase, and I know that this didn't work for us when using tombatossals/angular-leaflet-directive.

[vmvini]

You can set the maxNativeZoom like this:

vm.tiles = { url: someUrl, options:{ maxNativeZoom: 18, maxZoom: 30 } };

And you reference this tile in <leaflet tiles="vm.tiles" >