WatcherManager leaks memory on un-rewatched nodes

[jahqueel]

When a watch fires, the WatcherManager keeps the node's path in its re-watch dictionaries instead of clearing it out like the Java client does.

This example will print out the watchManager dictionary after watching and triggering for 100 different nodes:

util = require('util');
zk = require('node-zookeeper-client');

server = process.env.ZOOKEEPER_ADDRESS
testBasePath = '/test';
watchesToLeak = 100;

client = zk.createClient(server);
client.once('connected', function() {
  client.mkdirp(testBasePath, function(err, path) {
    asplode(watchesToLeak);
  });
});
client.connect();

function asplode(i) {
  client.create(testBasePath + '/i-', zk.CreateMode.EPHEMERAL_SEQUENTIAL, function(err, path) {
    client.exists(path, function(ev) {
      console.log(path + " " + ev.getName());
    }, function(err, stat) {
      client.remove(path, function(err) {
        if(i > 0) asplode(i - 1);
        else {
          console.log(util.inspect(client.connectionManager.watcherManager));
          client.close();
        }
      });
    });
  });
}

[jahqueel]

The simple fix in #33 is working for me.