Bump mpath from 0.5.2 to 0.8.4 (#101)

Bumps [mpath](https://github.com/aheckmann/mpath) from 0.5.2 to 0.8.4.
- [Release notes](https://github.com/aheckmann/mpath/releases)
- [Changelog](https://github.com/aheckmann/mpath/blob/master/History.md)
- [Commits](mongoosejs/mpath@0.5.2...0.8.4)

---
updated-dependencies:
- dependency-name: mpath
  dependency-type: direct:production
...

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package.json

@@ -32,7 +32,7 @@
     "buffer-equal-constant-time": "^1.0.1",
     "dotty": "~0.1.0",
     "json-stable-stringify": "^1.0.0",
-    "mpath": "^0.5.1",
+    "mpath": "^0.8.4",
     "semver": "^5.5.0",
     "underscore": "^1.5.0"
   },