Specify UTF-8 charset in Content-Type

The default HTTP charset is ISO-8859-1 so we need to specify UTF-8,
which is what is being sent to the client.

Author: mangefoo

AndroidAsync/src/com/koushikdutta/async/http/server/AsyncHttpServerResponseImpl.java

@@ -128,7 +128,7 @@ public void send(String contentType, String string) {
             mContentLength = bytes.length;
             mRawHeaders.set("Content-Length", Integer.toString(bytes.length));
             mRawHeaders.set("Content-Type", contentType);
-            
+
             writeHead();
             mSink.write(ByteBuffer.wrap(string.getBytes()));
             onEnd();
@@ -150,12 +150,12 @@ protected void report(Exception e) {
     @Override
     public void send(String string) {
         responseCode(200);
-        send("text/html", string);
+        send("text/html; charset=utf8", string);
     }
 
     @Override
     public void send(JSONObject json) {
-        send("application/json", json.toString());
+        send("application/json; charset=utf8", json.toString());
     }
 
     public void sendFile(File file) {