bump dependencies

package.json

@@ -31,22 +31,22 @@
     "abstract-leveldown": "~2.4.0",
     "bindings": "~1.2.1",
     "fast-future": "~1.0.0",
-    "nan": "~2.0.0",
+    "nan": "~2.1.0",
     "prebuild": "^2.7.0"
   },
   "devDependencies": {
-    "async": "~1.0.0",
+    "async": "~1.5.0",
     "delayed": "~1.0.1",
     "du": "~0.1.0",
     "faucet": "0.0.1",
-    "mkfiletree": "~0.0.1",
+    "mkfiletree": "~1.0.1",
     "monotonic-timestamp": "~0.0.8",
     "node-uuid": "~1.4.3",
     "optimist": "~0.6.1",
     "readfiletree": "~0.0.1",
-    "rimraf": "~2.2.8",
+    "rimraf": "~2.4.4",
     "slump": "~2.0.0",
-    "tape": "~4.0.0"
+    "tape": "~4.2.2"
   },
   "scripts": {
     "install": "prebuild --download",