Parse delimited from test

Hi, I need to parse multiple messages from one file. In Google protocol buffers I used [parseDelimetedFrom](https://developers.google.com/protocol-buffers/docs/reference/java/com/google/protobuf/AbstractParser#parseDelimitedFrom(java.io.InputStream)). This is my attempt to implement same method wire-way.
So, you suggest to change
```java
byte[] toByteArray(M message) {
    byte[] result = new byte[getSerializedSize(message)];
    try {
      write(message, WireOutput.newInstance(result));
    } catch (IOException e) {
      throw new RuntimeException(e);
    }
    return result;
  }
```
to
```java
  byte[] toByteArray(M message) {
    Buffer buffer = new Buffer();
    try {
      write(message, WireOutput.newInstance(buffer));
    } catch (IOException e) {
      throw new RuntimeException(e);
    }
    return buffer.readByteArray();
  }
```
I can't find another method to determine when writing to WireOutput is over.