sprite load delay

[incanus]

I'm curious @kkaefer if you've thought at all about the sprite load delay. I'm seeing this also impacting #60 because Maki comes down with it as well. On my system, it can sometimes take a few seconds for the sprite to come down and things to pop into place.

Longer term, each map style would likely have a texture atlas sprite, though we could pre-bundle Maki and other common resources locally.

Seems like for now, we could bundle the sprite atlas with the source since our style is also local.

[incanus]

Per resolution of mapbox/mapbox-gl-js#358 this may get specified in the style and could be pointed at local or remote sources.

[incanus]

Superseded by #144.