Upgrade netty to 4.1.5.Final (#547)

Author: NiteshKant

gradle.properties

@@ -13,5 +13,5 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 #
-netty_version=4.1.0.Final
+netty_version=4.1.5.Final
 slf4j_version=1.7.6

rxnetty-http/src/main/java/io/reactivex/netty/protocol/http/ws/server/WebSocketHandshaker.java

@@ -73,7 +73,7 @@ protected static String selectSubprotocol(String requestedSubprotocols, String[]
             return null;
         }
 
-        String[] requestedSubprotocolArray = StringUtil.split(requestedSubprotocols, ',');
+        String[] requestedSubprotocolArray = requestedSubprotocols.split(",");
 
         for (String p: requestedSubprotocolArray) {
             String requestedSubprotocol = p.trim();