First sketch of using vtile.addImage.
Update fixture for buffer-ignoring addImage.
Add layer option to backend constructor for setting a vt image layer name.
Merge branch 'master' into raster-pbf

Conflicts:
	test/backend.js
	test/test.js
Add i@2x fixtures to demonstrate raster scaling.
Xray symbolizer for raster layers. Refs #58.
Force integers for z,x,y.
Use mapnik ~1.4.4
mapnik ~1.4.5
Less diff.
Finish nuking deflate flag.
Try replacing stringified buffers with hex encoding to normalize v0.8 and v0.10
Quick blind try at casting.
More blind tries.
Same interface to both.
Merge pull request #59 from mapbox/raster-pbf

Raster pbf