Support multibyte messages

Change-Id: I2e9e046fbd073b4bcd517b2d6d16fef43de426ae
(cherry picked from commit c3e5d6b6a74c4fdd27f7f49c2849002f9dd9d18c)

src/main/java/com/cisco/gerrit/plugins/slack/client/WebhookClient.java

diff --git a/src/main/java/com/cisco/gerrit/plugins/slack/client/WebhookClient.java b/src/main/java/com/cisco/gerrit/plugins/slack/client/WebhookClient.java
index 5ecb0fe..6f6ad56 100644
--- a/src/main/java/com/cisco/gerrit/plugins/slack/client/WebhookClient.java
+++ b/src/main/java/com/cisco/gerrit/plugins/slack/client/WebhookClient.java
@@ -110,7 +110,7 @@
                 DataOutputStream request;
                 request = new DataOutputStream(connection.getOutputStream());
 
-                request.writeBytes(message);
+                request.write(message.getBytes("UTF-8"));
                 request.flush();
                 request.close();
             }