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.
Yeah. The lack of parity with `WireInput` means we can't just do this:
```java
public void writeDelimitedTo(Sink sink) throws IOException {
  MessageAdapter<Message> adapter = WIRE.messageAdapter((Class<Message>) getClass());
  WireOutput output = WireOutput.newInstance(sink);
  output.writeVarint32(adapter.getSerializedSize(this));
  adapter.write(this, output);
}
```