Merge pull request AsyncHttpClient#1249 from doom369/master

AsyncHttpClient#1246 added "ThreadSafe" in comments section for DefaultAsyncHttpClient

Author: slandelle

client/src/main/java/org/asynchttpclient/DefaultAsyncHttpClient.java

@@ -33,6 +33,9 @@
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
+/**
+ * Default and threadsafe implementation of {@link AsyncHttpClient}.
+ */
 public class DefaultAsyncHttpClient implements AsyncHttpClient {
 
     private final static Logger LOGGER = LoggerFactory.getLogger(DefaultAsyncHttpClient.class);