Add readable ZXYStream and createZXYStream method. Refs #42.

lib/mbtiles.js

@@ -8,6 +8,7 @@ var Buffer = require('buffer').Buffer;
 var sm = new (require('sphericalmercator'));
 var sqlite3 = require('sqlite3');
 var tiletype = require('tiletype');
+var ZXYStream = require('./zxystream');
 
 function noop(err) {
     if (err) throw err;
@@ -740,3 +741,8 @@ MBTiles.prototype.geocoderCentroid = function(id, zxy, callback) {
         ], mid[0]));
     });
 };
+
+MBTiles.prototype.createZXYStream = function(options) {
+    return new ZXYStream(this, options);
+};
+