Add link to etcd-browser under Tools heading

Documentation/libraries-and-tools.md

@@ -5,6 +5,7 @@
 - [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
+- [etcd-browser](https://github.com/henszey/etcd-browser) - A web-based key/value editor for etcd using AngularJS
 
 **Go libraries**