Add etcd-fs as a tool

Documentation/libraries-and-tools.md

@@ -4,6 +4,7 @@
 
 - [etcdctl](https://github.com/coreos/etcdctl) - A command line client for etcd
 - [etcd-dump](https://npmjs.org/package/etcd-dump) - Command line utility for dumping/restoring etcd.
+- [etcd-fs](https://github.com/xetorthio/etcd-fs) - FUSE filesystem for etcd
 
 **Go libraries**