Update RELEASE_NOTES.md

Author: xerial

RELEASE_NOTES.md

@@ -3,8 +3,8 @@
 * 0.8.0
  * Split MessagePack.Config into MessagePack.Packer/UnpackerConfig 
  * Changed MessageBuffer API 
-   * It allows releasing the previously allocated buffers upon MessageBufferInput.next() call.
-   * MessageBufferOutput now can read data from external byte arrays
+    * It allows releasing the previously allocated buffers upon MessageBufferInput.next() call.
+    * MessageBufferOutput now can read data from external byte arrays
  * MessagePacker supports addPayload(byte[]) to feed the data from an external data source 
    * This saves the cost of copying large data to the internal message buffer
  * Performance improvement of packString