Merge pull request #7 from square/jw/okio-writer

Always buffer sink.

moshi/src/main/java/com/squareup/moshi/JsonWriter.java

@@ -187,12 +187,8 @@ public class JsonWriter implements Closeable, Flushable {
     if (sink == null) {
       throw new NullPointerException("sink == null");
     }
-    if (sink instanceof BufferedSink) {
-      this.sink = (BufferedSink) sink;
-    } else {
     this.sink = Okio.buffer(sink);
   }
-  }
 
   /**
    * Sets the indentation string to be repeated for each level of indentation