Merge pull request #100 from pusher/fix-97

Make connection event listeners concurrent hashmap. Resolves #97

Author: jpatel531

src/main/java/com/pusher/client/connection/websocket/WebSocketConnection.java

@@ -7,6 +7,7 @@
 import java.util.HashSet;
 import java.util.Map;
 import java.util.Set;
+import java.util.concurrent.ConcurrentHashMap;
 import java.util.concurrent.Future;
 import java.util.concurrent.TimeUnit;
 
@@ -33,7 +34,7 @@ public class WebSocketConnection implements InternalConnection, WebSocketListene
 
     private final Factory factory;
     private final ActivityTimer activityTimer;
-    private final Map<ConnectionState, Set<ConnectionEventListener>> eventListeners = new HashMap<ConnectionState, Set<ConnectionEventListener>>();
+    private final Map<ConnectionState, Set<ConnectionEventListener>> eventListeners = new ConcurrentHashMap<ConnectionState, Set<ConnectionEventListener>>();
     private final URI webSocketUri;
     private final Proxy proxy;