Switch to Level/deferred-leveldown master

Author: vweevers

package.json

@@ -14,7 +14,7 @@
     "prepublishOnly": "npm run dependency-check"
   },
   "dependencies": {
-    "deferred-leveldown": "github:Level/deferred-leveldown#greenkeeper/abstract-leveldown-6.1.0",
+    "deferred-leveldown": "github:Level/deferred-leveldown",
     "level-errors": "~2.0.0",
     "level-iterator-stream": "~4.0.0",
     "xtend": "~4.0.0"